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All questions of Meiosis and Genetic Variability (BIO) for MCAT Exam
Which of the following conditions is called monosomic?- a)n + 1
- b)2n + 1
- c)2n + 2
- d)2n − 1
Correct answer is option 'D'. Can you explain this answer?
Which of the following conditions is called monosomic?
a)
n + 1
b)
2n + 1
c)
2n + 2
d)
2n − 1
|
Anjana Sharma answered |
Monosomics (2n - 1) one chromosomes less then diploid set of somatic chromosome number.
In meiosis, the daughter cells are not similar to the parent because of- a)Crossing over
- b)Synapsis
- c)Both 1 and 2 above
- d)None of the above
Correct answer is 'A'. Can you explain this answer?
In meiosis, the daughter cells are not similar to the parent because of
a)
Crossing over
b)
Synapsis
c)
Both 1 and 2 above
d)
None of the above
|
Rajeev Saxena answered |
Meiosis is basically an extended and complex version of mitosis. The term “Reductional division” gives this process the underlying definition, a sequence of events that results in reduction of the total number of chromosomes (from a diploid state of 46 to a haploid state of 23; in general, from ‘2n’ to ‘n’).
However, in the initial steps of meiosis, there is an eventful period wherein the previously duplicated chromosomes (in the S-Phase or Synthesis phase of cell cycle) exchange a part of their respective genetic material, a process termed as Recombination through crossing over (of the genetic material). The further steps are the same as in mitosis, but because of the exchange, the daughter chromosomes will have a different identity than their parents.
Klinefelter’s syndrome is due to- a)One Y only
- b)One X only
- c)Two X and one Y
- d)One X and two Y
Correct answer is option 'C'. Can you explain this answer?
Klinefelter’s syndrome is due to
a)
One Y only
b)
One X only
c)
Two X and one Y
d)
One X and two Y
|
Kritika Singh answered |
In klinefelter syndrome One X chromosome increases... show the situation is XXY
Crossing over may result in- a)Addition of genetic material
- b)Deletion of genetic material
- c)Exchange of genetic material
- d)All of the above
Correct answer is option 'C'. Can you explain this answer?
Crossing over may result in
a)
Addition of genetic material
b)
Deletion of genetic material
c)
Exchange of genetic material
d)
All of the above
|
Vijay Bansal answered |
Crossing over is the exchange of genes between two chromosomes, resulting in non-identical chromatids that comprise the genetic material of gametes. This process occurs during Prophase I of Meiosis, just prior to chromosome alignment and splitting of the cell.
Down’s syndrome is due to- a)Linkage
- b)Non-disjunction of chromosome
- c)Crossing over
- d)Sex-linked inheritance
Correct answer is option 'B'. Can you explain this answer?
Down’s syndrome is due to
a)
Linkage
b)
Non-disjunction of chromosome
c)
Crossing over
d)
Sex-linked inheritance
|
Lakshmi Pillai answered |
Explanation:
Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristic features of Down syndrome.
Non-disjunction of chromosome:
The most common cause of Down syndrome is non-disjunction of chromosome 21 during meiosis. Non-disjunction occurs when the chromosomes fail to separate properly during cell division, resulting in an abnormal distribution of chromosomes in the resulting cells. In the case of Down syndrome, non-disjunction of chromosome 21 occurs either during the formation of the egg or sperm, resulting in an extra copy of chromosome 21 in the fertilized egg.
Key Points:
- Non-disjunction of chromosome 21 during meiosis is the most common cause of Down syndrome.
- Non-disjunction can occur during the formation of the egg or sperm.
- Non-disjunction leads to an abnormal distribution of chromosomes in the resulting cells, resulting in an extra copy of chromosome 21.
Other Causes:
While non-disjunction is the primary cause of Down syndrome, there are other rare genetic variations that can also result in the condition. These include translocation, mosaicism, and partial trisomy.
- Translocation: In some cases, a piece of chromosome 21 breaks off and attaches to another chromosome, typically chromosome 14. This is called a translocation. If a person has a translocation involving chromosome 21, they may have a higher risk of having a child with Down syndrome.
- Mosaicism: Mosaicism occurs when there is a mixture of cells with a normal number of chromosomes and cells with an extra copy of chromosome 21. This can result in milder symptoms or features of Down syndrome.
- Partial Trisomy: In rare cases, a person may have only a portion of chromosome 21 duplicated, leading to a condition known as partial trisomy. This can result in a milder form of Down syndrome, as only a subset of genes on chromosome 21 is affected.
Conclusion:
In conclusion, the most common cause of Down syndrome is non-disjunction of chromosome 21 during meiosis. This results in an extra copy of chromosome 21 in the fertilized egg, leading to the characteristic features of Down syndrome. Other rare genetic variations, such as translocation, mosaicism, and partial trisomy, can also result in Down syndrome but are less common.
Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristic features of Down syndrome.
Non-disjunction of chromosome:
The most common cause of Down syndrome is non-disjunction of chromosome 21 during meiosis. Non-disjunction occurs when the chromosomes fail to separate properly during cell division, resulting in an abnormal distribution of chromosomes in the resulting cells. In the case of Down syndrome, non-disjunction of chromosome 21 occurs either during the formation of the egg or sperm, resulting in an extra copy of chromosome 21 in the fertilized egg.
Key Points:
- Non-disjunction of chromosome 21 during meiosis is the most common cause of Down syndrome.
- Non-disjunction can occur during the formation of the egg or sperm.
- Non-disjunction leads to an abnormal distribution of chromosomes in the resulting cells, resulting in an extra copy of chromosome 21.
Other Causes:
While non-disjunction is the primary cause of Down syndrome, there are other rare genetic variations that can also result in the condition. These include translocation, mosaicism, and partial trisomy.
- Translocation: In some cases, a piece of chromosome 21 breaks off and attaches to another chromosome, typically chromosome 14. This is called a translocation. If a person has a translocation involving chromosome 21, they may have a higher risk of having a child with Down syndrome.
- Mosaicism: Mosaicism occurs when there is a mixture of cells with a normal number of chromosomes and cells with an extra copy of chromosome 21. This can result in milder symptoms or features of Down syndrome.
- Partial Trisomy: In rare cases, a person may have only a portion of chromosome 21 duplicated, leading to a condition known as partial trisomy. This can result in a milder form of Down syndrome, as only a subset of genes on chromosome 21 is affected.
Conclusion:
In conclusion, the most common cause of Down syndrome is non-disjunction of chromosome 21 during meiosis. This results in an extra copy of chromosome 21 in the fertilized egg, leading to the characteristic features of Down syndrome. Other rare genetic variations, such as translocation, mosaicism, and partial trisomy, can also result in Down syndrome but are less common.
Meiosis results in
- a)Production of gametes
- b)Reduction in Chromosome number
- c)Introduction of variation
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
Meiosis results in
a)
Production of gametes
b)
Reduction in Chromosome number
c)
Introduction of variation
d)
All of the above
|
|
Anjali Iyer answered |
As previously mentioned, the first round of nuclear division that occurs during the formation of gametes is called meiosis I. It is also known as the reduction division because it results in cells that have half the number of chromosomes as the parent cell.
Match List I and List II, and select the correct answer.
- a)1, 2 and 3 are correct.
- b)1 and 3 are correct.
- c)2 and 4 are correct.
- d)Only 1 is correct.
Correct answer is option 'D'. Can you explain this answer?
Match List I and List II, and select the correct answer.
a)
1, 2 and 3 are correct.
b)
1 and 3 are correct.
c)
2 and 4 are correct.
d)
Only 1 is correct.
|
Trisha Vashisht answered |
Correct Answer :- d
Explanation : Genetic variation comes from crossing over, which may occur during prophase I of meiosis.
In prophase I of meiosis, the replicated homologous pair of chromosomes comes together in the process called synapsis, and sections of the chromosomes are exchanged.
Mutations which arise suddenly in nature are called- a)Spontaneous mutations
- b)Gene mutations
- c)Induced mutations
- d)Chromosomal mutations
Correct answer is option 'A'. Can you explain this answer?
Mutations which arise suddenly in nature are called
a)
Spontaneous mutations
b)
Gene mutations
c)
Induced mutations
d)
Chromosomal mutations
|
Pooja Mehta answered |
Gene mutation is defined as a sudden discrete change in the genetic material of gene which is heritable. Mutations when they arise suddenly in nature are called spontaneous mutations.
Synapsis occurs in which of the following stages of meiosis?- a)Diakinesis
- b)Pachytene
- c)Leptotene
- d)Zygotene
Correct answer is option 'D'. Can you explain this answer?
Synapsis occurs in which of the following stages of meiosis?
a)
Diakinesis
b)
Pachytene
c)
Leptotene
d)
Zygotene
|
|
Vijay Bansal answered |
Most of the events that function to differentiate meiosis from mitosis occur in Prophase I
Homologous chromosomes form bivalents (or tetrads) and crossing over occurs between non-sister chromatids
Prophase I is divided into 5 distinctive sub-stages:
1. Leptotene – The chromosomes begin to condense and are attached to the nuclear membrane via their telomeres
2. Zygotene – Synapsis begins with a synaptonemal complex forming between homologous chromosomes
3. Pachytene – Crossing over of genetic material occurs between non-sister chromatids
4. Diplotene – Synapsis ends with disappearance of synaptonemal complex; homologous pairs remain attached at chiasmata
5. Diakinesis – Chromosomes become fully condensed and nuclear membrane disintegrates prior to metaphase I
Synaptonemal complex is observed during cell division in- a)Meiotic prophase
- b)Mitotic prophase
- c)Meiotic metaphase
- d)Mitotic telophase
Correct answer is option 'A'. Can you explain this answer?
Synaptonemal complex is observed during cell division in
a)
Meiotic prophase
b)
Mitotic prophase
c)
Meiotic metaphase
d)
Mitotic telophase
|
Imk Pathsala answered |
The formation of tetrad is a special characteristic of Prophase 1 of meiosis 1.
The homologous pair aligns with each other and gets ready for crossing over.
So, the correct option is 'Meiotic Prophase'.
The homologous pair aligns with each other and gets ready for crossing over.
So, the correct option is 'Meiotic Prophase'.
Turner syndrome is- a)XYY
- b)XO
- c)XXX
- d)XXY
Correct answer is option 'B'. Can you explain this answer?
Turner syndrome is
a)
XYY
b)
XO
c)
XXX
d)
XXY
|
Ishani Nambiar answered |
Turner syndrome (TS), also known 45,X, or 45,X0, is a genetic condition in which a female is partly or completely missing an X chromosome. Signs and symptoms vary among those affected.
When synapsis is complete all along the chromosome, the cell is said to have entered a stage called- a)Diakinesis
- b)Zygotene
- c)Diplotene
- d)Pachytene
Correct answer is option 'D'. Can you explain this answer?
When synapsis is complete all along the chromosome, the cell is said to have entered a stage called
a)
Diakinesis
b)
Zygotene
c)
Diplotene
d)
Pachytene
|
Surbhi Dasgupta answered |
Pachytene Stage in Meiosis
The process of meiosis is divided into several stages, one of which is the Pachytene stage. This stage occurs during the first meiotic division or meiosis I. During this stage, homologous chromosomes pair up and form structures called bivalents or tetrads. The Pachytene stage is characterized by the following events:
Synapsis
During the Pachytene stage, homologous chromosomes pair up and form structures called bivalents or tetrads. This process is called synapsis. The synaptonemal complex plays a crucial role in this process. The complex is composed of proteins that hold the homologous chromosomes together.
Crossing over
Crossing over occurs during the Pachytene stage. It is the exchange of genetic material between homologous chromosomes. This process results in the creation of new combinations of genes, which contributes to genetic diversity.
Chiasmata formation
During the Pachytene stage, the homologous chromosomes that have paired up undergo crossing over. This process results in the formation of chiasmata, which are visible under a microscope. Chiasmata are the points where the homologous chromosomes crisscross and exchange genetic material.
Conclusion
When synapsis is complete all along the chromosome, the cell is said to have entered a stage called Pachytene. During this stage, homologous chromosomes pair up and form bivalents or tetrads. Synapsis, crossing over, and chiasmata formation occur during this stage. The Pachytene stage is an essential process in meiosis as it contributes to the genetic diversity of offspring.
The process of meiosis is divided into several stages, one of which is the Pachytene stage. This stage occurs during the first meiotic division or meiosis I. During this stage, homologous chromosomes pair up and form structures called bivalents or tetrads. The Pachytene stage is characterized by the following events:
Synapsis
During the Pachytene stage, homologous chromosomes pair up and form structures called bivalents or tetrads. This process is called synapsis. The synaptonemal complex plays a crucial role in this process. The complex is composed of proteins that hold the homologous chromosomes together.
Crossing over
Crossing over occurs during the Pachytene stage. It is the exchange of genetic material between homologous chromosomes. This process results in the creation of new combinations of genes, which contributes to genetic diversity.
Chiasmata formation
During the Pachytene stage, the homologous chromosomes that have paired up undergo crossing over. This process results in the formation of chiasmata, which are visible under a microscope. Chiasmata are the points where the homologous chromosomes crisscross and exchange genetic material.
Conclusion
When synapsis is complete all along the chromosome, the cell is said to have entered a stage called Pachytene. During this stage, homologous chromosomes pair up and form bivalents or tetrads. Synapsis, crossing over, and chiasmata formation occur during this stage. The Pachytene stage is an essential process in meiosis as it contributes to the genetic diversity of offspring.
Match the items of Column - I with Column - II:
Column-I Column-II
(a) XX-XO method of sex determination (i) Turner's syndrome
(b) XX-XY method of sex determination (ii) Female heterogametic
(c) Karyotype-45 (iii) Grasshopper
(d) ZW-ZZ method of sex determination (iv) Female homogametic
Select the correct option from the following:- a)(a) - (ii), (b) - (iv), (c) - (i), (d) - (iii)
- b)(a) - (i), (b) - (iv), (c) - (ii), (d) - (iii)
- c)(a) - (iii), (b) - (iv), (c) - (i), (d) - (ii)
- d)(a) - (iv), (b) - (ii), (c) - (i), (d) - (iii)
Correct answer is option 'C'. Can you explain this answer?
Match the items of Column - I with Column - II:
Column-I Column-II
(a) XX-XO method of sex determination (i) Turner's syndrome
(b) XX-XY method of sex determination (ii) Female heterogametic
(c) Karyotype-45 (iii) Grasshopper
(d) ZW-ZZ method of sex determination (iv) Female homogametic
Select the correct option from the following:
Column-I Column-II
(a) XX-XO method of sex determination (i) Turner's syndrome
(b) XX-XY method of sex determination (ii) Female heterogametic
(c) Karyotype-45 (iii) Grasshopper
(d) ZW-ZZ method of sex determination (iv) Female homogametic
Select the correct option from the following:
a)
(a) - (ii), (b) - (iv), (c) - (i), (d) - (iii)
b)
(a) - (i), (b) - (iv), (c) - (ii), (d) - (iii)
c)
(a) - (iii), (b) - (iv), (c) - (i), (d) - (ii)
d)
(a) - (iv), (b) - (ii), (c) - (i), (d) - (iii)
|
Mahi Menon answered |
Explanation:
XX-XO method of sex determination:
- In this method, females have a pair of XX chromosomes, while males have a single X chromosome (XO).
- This method is observed in grasshoppers, where females are heterogametic (XX) and males are homogametic (XO).
XX-XY method of sex determination:
- In this method, females have a pair of XX chromosomes, while males have XY chromosomes.
- This method is commonly observed in humans and other mammals, where females are homogametic (XX) and males are heterogametic (XY).
Karyotype-45:
- This refers to Turner syndrome, a condition in females where one of the X chromosomes is missing or partially missing.
- Individuals with Turner syndrome typically have a karyotype of 45,XO, leading to various developmental and physical abnormalities.
ZW-ZZ method of sex determination:
- In this method, females have ZW chromosomes, while males have ZZ chromosomes.
- This method is observed in certain bird species, where females are heterogametic (ZW) and males are homogametic (ZZ).
Therefore, the correct match for the items in Column I with Column II is:
- (a) - (iii) Karyotype-45 (Turner syndrome)
- (b) - (iv) ZW-ZZ method of sex determination
- (c) - (i) XX-XO method of sex determination (Grasshopper)
- (d) - (ii) XX-XY method of sex determination
Thus, option (c) - (a) - (iii), (b) - (iv), (c) - (i), (d) - (ii) is the correct answer.
XX-XO method of sex determination:
- In this method, females have a pair of XX chromosomes, while males have a single X chromosome (XO).
- This method is observed in grasshoppers, where females are heterogametic (XX) and males are homogametic (XO).
XX-XY method of sex determination:
- In this method, females have a pair of XX chromosomes, while males have XY chromosomes.
- This method is commonly observed in humans and other mammals, where females are homogametic (XX) and males are heterogametic (XY).
Karyotype-45:
- This refers to Turner syndrome, a condition in females where one of the X chromosomes is missing or partially missing.
- Individuals with Turner syndrome typically have a karyotype of 45,XO, leading to various developmental and physical abnormalities.
ZW-ZZ method of sex determination:
- In this method, females have ZW chromosomes, while males have ZZ chromosomes.
- This method is observed in certain bird species, where females are heterogametic (ZW) and males are homogametic (ZZ).
Therefore, the correct match for the items in Column I with Column II is:
- (a) - (iii) Karyotype-45 (Turner syndrome)
- (b) - (iv) ZW-ZZ method of sex determination
- (c) - (i) XX-XO method of sex determination (Grasshopper)
- (d) - (ii) XX-XY method of sex determination
Thus, option (c) - (a) - (iii), (b) - (iv), (c) - (i), (d) - (ii) is the correct answer.
Gene for colour blindness is located on- a)13th chromosome
- b)Y chromosome
- c)21st chromosome
- d)X chromosome
Correct answer is option 'D'. Can you explain this answer?
Gene for colour blindness is located on
a)
13th chromosome
b)
Y chromosome
c)
21st chromosome
d)
X chromosome
|
Asha Chauhan answered |
Introduction:
Color blindness is a genetic disorder that impairs a person's ability to perceive certain colors, usually red and green. It is caused by a genetic mutation that affects the cones in the retina of the eye, which are responsible for color vision. This mutation is located on the X chromosome.
Explanation:
1. Genetic Basis of Color Blindness:
Color blindness is an X-linked recessive genetic disorder. This means that the gene responsible for color blindness is located on the X chromosome. The X chromosome is one of the two sex chromosomes, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY). Since the gene for color blindness is located on the X chromosome, it primarily affects males.
2. X Chromosome and Inheritance:
The X chromosome carries many genes that are responsible for various traits and characteristics. In males, the Y chromosome does not have a corresponding allele for the genes on the X chromosome. Therefore, if a male inherits a mutated gene on the X chromosome, he will express the trait associated with that gene, as there is no second copy of the gene to mask its effects.
3. Inheritance Pattern of Color Blindness:
When a female carries a mutated gene on one of her X chromosomes, she is considered a carrier. As carriers have a normal copy of the gene on their other X chromosome, they do not exhibit color blindness themselves but can pass the mutated gene to their offspring. If a carrier female has a son, there is a 50% chance that he will inherit the mutated gene and be color blind.
4. Higher Prevalence in Males:
Since males have only one X chromosome, they are more susceptible to color blindness. If a male inherits the mutated gene on his X chromosome, he will be color blind. On the other hand, females need to inherit the mutated gene on both of their X chromosomes to be color blind. This is why color blindness is more commonly seen in males.
Conclusion:
The gene for color blindness is located on the X chromosome. This genetic disorder primarily affects males due to the inheritance pattern of the X chromosome. Understanding the genetic basis of color blindness helps in diagnosing and managing the condition effectively.
Color blindness is a genetic disorder that impairs a person's ability to perceive certain colors, usually red and green. It is caused by a genetic mutation that affects the cones in the retina of the eye, which are responsible for color vision. This mutation is located on the X chromosome.
Explanation:
1. Genetic Basis of Color Blindness:
Color blindness is an X-linked recessive genetic disorder. This means that the gene responsible for color blindness is located on the X chromosome. The X chromosome is one of the two sex chromosomes, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY). Since the gene for color blindness is located on the X chromosome, it primarily affects males.
2. X Chromosome and Inheritance:
The X chromosome carries many genes that are responsible for various traits and characteristics. In males, the Y chromosome does not have a corresponding allele for the genes on the X chromosome. Therefore, if a male inherits a mutated gene on the X chromosome, he will express the trait associated with that gene, as there is no second copy of the gene to mask its effects.
3. Inheritance Pattern of Color Blindness:
When a female carries a mutated gene on one of her X chromosomes, she is considered a carrier. As carriers have a normal copy of the gene on their other X chromosome, they do not exhibit color blindness themselves but can pass the mutated gene to their offspring. If a carrier female has a son, there is a 50% chance that he will inherit the mutated gene and be color blind.
4. Higher Prevalence in Males:
Since males have only one X chromosome, they are more susceptible to color blindness. If a male inherits the mutated gene on his X chromosome, he will be color blind. On the other hand, females need to inherit the mutated gene on both of their X chromosomes to be color blind. This is why color blindness is more commonly seen in males.
Conclusion:
The gene for color blindness is located on the X chromosome. This genetic disorder primarily affects males due to the inheritance pattern of the X chromosome. Understanding the genetic basis of color blindness helps in diagnosing and managing the condition effectively.
Which of the following is the correct sequence for a meiotic cell cycle?
S → G1 → G2 → M → S
G1 → S → G2 → M → G1
G2 → G1 → S → M → G2
G1 → G2 → S → M → G2- a)A
- b)B
- c)C
- d)D
Correct answer is option 'B'. Can you explain this answer?
Which of the following is the correct sequence for a meiotic cell cycle?
S → G1 → G2 → M → S
G1 → S → G2 → M → G1
G2 → G1 → S → M → G2
G1 → G2 → S → M → G2
S → G1 → G2 → M → S
G1 → S → G2 → M → G1
G2 → G1 → S → M → G2
G1 → G2 → S → M → G2
a)
A
b)
B
c)
C
d)
D
|
Sagar Singh answered |
Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis, Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis
Cross-like configurations when non-sister chromatids of a bivalent come in contact during the first meiotic division are- a)Chiasmata
- b)Chromomeres
- c)Bivalents
- d)Centromeres
Correct answer is option 'A'. Can you explain this answer?
Cross-like configurations when non-sister chromatids of a bivalent come in contact during the first meiotic division are
a)
Chiasmata
b)
Chromomeres
c)
Bivalents
d)
Centromeres
|
|
Rohan Singh answered |
Chiasmata) is the point of contact, the physical link, between two (non-sister) chromatids belonging to homologous chromosomes. At a given chiasma, an exchange of genetic material can occur between both chromatids, what is called a chromosomal crossover, but this is much more frequent during meiosis than mitosis.
The chromosomal basis of sex determination was discovered by which of the following scientists?- a)Stevens
- b)Grey
- c)Henking
- d)Wilson
Correct answer is option 'C'. Can you explain this answer?
The chromosomal basis of sex determination was discovered by which of the following scientists?
a)
Stevens
b)
Grey
c)
Henking
d)
Wilson
|
Saumya Sarkar answered |
The scientist who discovered the chromosomal basis of sex determination is Nettie Stevens.
Which of the following determines the sex of the offspring in male heterogametic conditions?- a)Egg
- b)Sperm
- c)Both egg and sperm
- d)It cannot be determined
Correct answer is option 'B'. Can you explain this answer?
Which of the following determines the sex of the offspring in male heterogametic conditions?
a)
Egg
b)
Sperm
c)
Both egg and sperm
d)
It cannot be determined
|
|
Akriti Gill answered |
Sperm is correct ans
in sperm ,XY chromosome are present
in egg ,XX chromosome are present
female ke similar gamete i.e.X&X hoge while male ke different i.e. X &Y hoge
isliye sperm male heterogametic condition show krta hai
in sperm ,XY chromosome are present
in egg ,XX chromosome are present
female ke similar gamete i.e.X&X hoge while male ke different i.e. X &Y hoge
isliye sperm male heterogametic condition show krta hai
Which of the following does not show XY type of male heterogametic condition?- a)Drosophila
- b)Human beings
- c)Elephants
- d)Grasshoppers
Correct answer is option 'D'. Can you explain this answer?
Which of the following does not show XY type of male heterogametic condition?
a)
Drosophila
b)
Human beings
c)
Elephants
d)
Grasshoppers
|
|
Ananya Das answered |
Grasshoppers do not show XY type of male heterogametic condition. XY type of male heterogametic condition is shown by a number of insects like Drosophila and mammals including human beings and elephants, the males in this type bear two types of sex chromosomes- X and Y type.
Select the incorrect statement:- a)Human males have one of their sex-chromosome much shorter than the other.
- b)Male fruit fly is heterogametic.
- c)In male grasshoppers, 50% of sperms have no sex chromosome.
- d)In domesticated fowls, the sex of progeny depends on the type of sperm rather than the egg.
Correct answer is option 'D'. Can you explain this answer?
a)
Human males have one of their sex-chromosome much shorter than the other.
b)
Male fruit fly is heterogametic.
c)
In male grasshoppers, 50% of sperms have no sex chromosome.
d)
In domesticated fowls, the sex of progeny depends on the type of sperm rather than the egg.
|
EduRev NEET answered |
In domesticated fowls (birds), the sex of the progeny is determined by the type of egg rather than the sperm. Female birds have two types of sex chromosomes (ZW) and males have two Z chromosomes (ZZ). Therefore, Option D is incorrect as the sex of progeny depends on the type of egg, not the sperm.
In sickle cell anaemia, glutamic acid is replaced by valine. Which one of the following triplets codes valine?- a)A A G
- b)G A A
- c)G G G
- d)G U G
Correct answer is option 'D'. Can you explain this answer?
In sickle cell anaemia, glutamic acid is replaced by valine. Which one of the following triplets codes valine?
a)
A A G
b)
G A A
c)
G G G
d)
G U G
|
|
Rajat Kapoor answered |
The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the betaglobin gene from GAG (Glutamic acid) to GUG (Valine).
Sickle-cell anaemia is- a)X-linked recessive inheritance
- b)Autosomal dominant inheritance
- c)Autosomal recessive inheritance
- d)X-linked dominant inheritance
Correct answer is option 'C'. Can you explain this answer?
Sickle-cell anaemia is
a)
X-linked recessive inheritance
b)
Autosomal dominant inheritance
c)
Autosomal recessive inheritance
d)
X-linked dominant inheritance
|
|
Pooja Mehta answered |
Autosomal recessive inheritance means that the gene is located on one of the autosomes (chromosome pairs 1 through 22). This means that males and females are equally affected. "Recessive" means that two copies of the gene are necessary to have the trait, one inherited from the mother, and one from the father.
Examples of autosomal recessive disorders include cystic fibrosis, sickle cell anemia, and Tay Sachs disease.
Sickle-cell anemia is an autosomal recessive genetic disorder whose carriers have a genetic advantage in surviving malaria. If 42% of the population is malaria resistant, but not anemic, what is frequency of the sickle-cell allele?- a)49%
- b)9%
- c)21%
- d)30%
Correct answer is option 'D'. Can you explain this answer?
Sickle-cell anemia is an autosomal recessive genetic disorder whose carriers have a genetic advantage in surviving malaria. If 42% of the population is malaria resistant, but not anemic, what is frequency of the sickle-cell allele?
a)
49%
b)
9%
c)
21%
d)
30%
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Orion Classes answered |
To determine the frequency of the sickle-cell allele, we can use the Hardy-Weinberg equation:
p2 + 2pq + q2 = 1
where:
p2 represents the frequency of individuals homozygous for the normal allele (not carrying the sickle-cell allele)
2pq represents the frequency of individuals heterozygous (carriers of the sickle-cell allele)
q2 represents the frequency of individuals homozygous for the sickle-cell allele
p2 represents the frequency of individuals homozygous for the normal allele (not carrying the sickle-cell allele)
2pq represents the frequency of individuals heterozygous (carriers of the sickle-cell allele)
q2 represents the frequency of individuals homozygous for the sickle-cell allele
Given that 42% of the population is malaria resistant but not anemic, which corresponds to the frequency of individuals homozygous for the normal allele (p2), we can calculate the frequency of the normal allele (p) using the square root:
p = √(0.42) ≈ 0.648
Since the sickle-cell allele is recessive, q = 1 - p:
q = 1 - 0.648 ≈ 0.352
The frequency of the sickle-cell allele is equal to 2pq:
2pq = 2(0.648)(0.352) ≈ 0.456
Therefore, the frequency of the sickle-cell allele is approximately 45.6%, which is closest to option D, 30%.
What is wrong with respect to sex determination in honey bees?- a)Unfertilized egg develops as a male by means of parthenogenesis.
- b)Union of sperm and egg develops as a female.
- c)All workers and males will have 16 chromosomes while queen will have 32 chromosomes.
- d)Males produce sperm by mitosis.
Correct answer is option 'C'. Can you explain this answer?
What is wrong with respect to sex determination in honey bees?
a)
Unfertilized egg develops as a male by means of parthenogenesis.
b)
Union of sperm and egg develops as a female.
c)
All workers and males will have 16 chromosomes while queen will have 32 chromosomes.
d)
Males produce sperm by mitosis.
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|
Mahi Menon answered |
Chromosome difference in honey bees
Honey bees have a unique sex determination system where females are diploid (having two sets of chromosomes) and males are haploid (having one set of chromosomes). This is different from most other organisms where males are typically the heterogametic sex.
Explanation of option C
The statement in option C is incorrect because all workers and males in honey bee colonies have 16 chromosomes, while the queen bee has 32 chromosomes. This difference in chromosome number is due to the process of haplodiploidy in honey bees.
Haplodiploidy in honey bees
In honey bees, fertilized eggs (resulting from the union of sperm and egg) develop into females (queens and workers) with two sets of chromosomes, while unfertilized eggs develop into males by means of parthenogenesis. Therefore, all females in a honey bee colony have 32 chromosomes, while males have 16 chromosomes.
Function of chromosomes in honey bees
The difference in chromosome number between males and females in honey bees plays a crucial role in their social structure and behavior. The haplodiploid sex determination system in honey bees is associated with the development of reproductive castes (queens and drones) and non-reproductive workers in the colony.
In conclusion, the statement in option C regarding chromosome number in honey bees is incorrect. It is important to understand the unique sex determination system in honey bees to appreciate their complex social organization and behavior.
Honey bees have a unique sex determination system where females are diploid (having two sets of chromosomes) and males are haploid (having one set of chromosomes). This is different from most other organisms where males are typically the heterogametic sex.
Explanation of option C
The statement in option C is incorrect because all workers and males in honey bee colonies have 16 chromosomes, while the queen bee has 32 chromosomes. This difference in chromosome number is due to the process of haplodiploidy in honey bees.
Haplodiploidy in honey bees
In honey bees, fertilized eggs (resulting from the union of sperm and egg) develop into females (queens and workers) with two sets of chromosomes, while unfertilized eggs develop into males by means of parthenogenesis. Therefore, all females in a honey bee colony have 32 chromosomes, while males have 16 chromosomes.
Function of chromosomes in honey bees
The difference in chromosome number between males and females in honey bees plays a crucial role in their social structure and behavior. The haplodiploid sex determination system in honey bees is associated with the development of reproductive castes (queens and drones) and non-reproductive workers in the colony.
In conclusion, the statement in option C regarding chromosome number in honey bees is incorrect. It is important to understand the unique sex determination system in honey bees to appreciate their complex social organization and behavior.
Which of the following is correct?- a)Henking discovered the small Y-chromosome.
- b)Drosophila also shows XX-XY sex determination like humans.
- c)Birds have ZZ-ZW sex determination, where females are ZZ and males are ZW.
- d)Grasshoppers show XX-XY sex determination.
Correct answer is option 'B'. Can you explain this answer?
Which of the following is correct?
a)
Henking discovered the small Y-chromosome.
b)
Drosophila also shows XX-XY sex determination like humans.
c)
Birds have ZZ-ZW sex determination, where females are ZZ and males are ZW.
d)
Grasshoppers show XX-XY sex determination.
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Top Rankers answered |
Drosophila, like humans, follows the XX-XY method of sex determination. Other options are incorrect; for example, in birds, females are ZW and males are ZZ. Henking discovered the X-chromosome and the term "X-body," not the Y-chromosome specifically.
Complete answer: Drosophila flies have chromosomes X and Y, and also autosomes. With exception of humans, Y-chromosomes will not confer masculinity, rather they compile the genes necessary for sperm production. Conversely, sex is defined as the ratio of X chromosomes to autosomes. Each cell ancestry in Drosophila takes a sexual decision all its own. One of the main approaches to illustrate this is by examining XX-XY mosaic flies, i.e. individual flies including a combination of XX and XY cells. Such mosaics reveal a mixture of male and female phenotypes, focusing on the genotype of each cell. The understanding of this variation here is that every Drosophila cell decides its sex independently. Three main genes are involved in the determination of sex in Drosophila. They're sex-lethal, sisterless, and deadpan. Deadpan is an autosomal gene that prevents sex-lethal, whereas the X chromosome is held by the sisterless and prevents the action of the deadpan.
So, the correct answer is an option (B).
Additional information:
Henking has uncovered the X-chromosomes. The work has been the result of a Leipzig research of the firebug testicle, and during that Henking realized that one chromosome did not engage in meiosis. Male grasshoppers are regarded as heterogametic because they create two distinct kinds of sperm cells: both with and without X chromosomes. Female grasshoppers seem to possess XX and grasshoppers will use XX- XO sex-determining system. The ZW sex-determination framework is a chromosome process that determines the sex of descendants in birds, or fish, and crustaceans, such as that of the gigantic river pomegranate, some insects, some invertebrates. In this, women with ZW chromosomes and men with ZZ chromosomes.
Note: Drosophila flies rely on biological evolution, which implies that mating needs male and female flies to produce children. Flies usually participate in courting or mating conduct, in which they copulate. The female then makes eggs, believing that she would eat enough already, and identify the correct medium to lay them.
So, the correct answer is an option (B).
Additional information:
Henking has uncovered the X-chromosomes. The work has been the result of a Leipzig research of the firebug testicle, and during that Henking realized that one chromosome did not engage in meiosis. Male grasshoppers are regarded as heterogametic because they create two distinct kinds of sperm cells: both with and without X chromosomes. Female grasshoppers seem to possess XX and grasshoppers will use XX- XO sex-determining system. The ZW sex-determination framework is a chromosome process that determines the sex of descendants in birds, or fish, and crustaceans, such as that of the gigantic river pomegranate, some insects, some invertebrates. In this, women with ZW chromosomes and men with ZZ chromosomes.
Note: Drosophila flies rely on biological evolution, which implies that mating needs male and female flies to produce children. Flies usually participate in courting or mating conduct, in which they copulate. The female then makes eggs, believing that she would eat enough already, and identify the correct medium to lay them.
During meiosis, crossover occurs between- a)Non-sister chromatids of non-homologous chromosomes
- b)Sister chromatids of homologous chromosomes
- c)Sister chromatids of non-homologous chromosomes
- d)Non-sister chromatids of homologous chromosomes
Correct answer is option 'D'. Can you explain this answer?
During meiosis, crossover occurs between
a)
Non-sister chromatids of non-homologous chromosomes
b)
Sister chromatids of homologous chromosomes
c)
Sister chromatids of non-homologous chromosomes
d)
Non-sister chromatids of homologous chromosomes
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Shibashish Das answered |
A gene, TALL, has recently been discovered that helps control the height that people will reach and results in taller than average height. Which of the following statements about this gene’s heritability are true?- a)If TALL has constant expressivity, every cell in the body will express the TALL protein
- b)If TALL has variable expressivity, everyone with the TALL gene will be tall
- c)If TALL has 50% penetrance, then only half the population has the TALL gene
- d)If TALL has 25% penetrance, it must be autosomal recessive
Correct answer is option 'B'. Can you explain this answer?
A gene, TALL, has recently been discovered that helps control the height that people will reach and results in taller than average height. Which of the following statements about this gene’s heritability are true?
a)
If TALL has constant expressivity, every cell in the body will express the TALL protein
b)
If TALL has variable expressivity, everyone with the TALL gene will be tall
c)
If TALL has 50% penetrance, then only half the population has the TALL gene
d)
If TALL has 25% penetrance, it must be autosomal recessive
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Orion Classes answered |
Variable expressivity refers to the phenomenon where individuals with the same genotype (in this case, carrying the TALL gene) can exhibit different phenotypes (in this case, different heights). It means that even though someone carries the TALL gene, other factors such as environmental influences or interactions with other genes can result in a range of heights among individuals.
Therefore, having the TALL gene does not guarantee that an individual will be tall, as the expression of the gene can vary and result in different heights.
A non-conservative mutation is one in which:- a)The new amino acid has different biochemical properties than the original
- b)A frameshift has occurred, causing production of a new amino acid
- c)A large segment of DNA is deleted
- d)No effect results in the protein
Correct answer is option 'A'. Can you explain this answer?
A non-conservative mutation is one in which:
a)
The new amino acid has different biochemical properties than the original
b)
A frameshift has occurred, causing production of a new amino acid
c)
A large segment of DNA is deleted
d)
No effect results in the protein
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Orion Classes answered |
Explanation: A non-conservative mutation is a type of genetic mutation that results in the substitution of one amino acid with a different amino acid during protein synthesis. In this type of mutation, the new amino acid has different biochemical properties, such as size, charge, hydrophobicity, or reactivity, compared to the original amino acid. This can have significant effects on the structure and function of the protein. In contrast, conservative mutations involve the substitution of an amino acid with another amino acid that has similar biochemical properties. Options B, C, and D are not accurate descriptions of a non-conservative mutation. Therefore, option A is the correct answer.
In which of the following organisms, the male heterogametic condition is not observed?- a)Grasshoppers
- b)Humans
- c)Drosophila
- d)Birds
Correct answer is option 'D'. Can you explain this answer?
In which of the following organisms, the male heterogametic condition is not observed?
a)
Grasshoppers
b)
Humans
c)
Drosophila
d)
Birds
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Hansa Sharma answered |
Birds do not show male heterogametic conditions. Instead, they show the female heterogametic condition. Male heterogametic condition is characterised by male individuals producing two different types of gametes.
What is the probability of having a girl child in sixth pregnancy if the first five progenies are boys?- a)25%
- b)50%
- c)65%
- d)10%
Correct answer is option 'B'. Can you explain this answer?
What is the probability of having a girl child in sixth pregnancy if the first five progenies are boys?
a)
25%
b)
50%
c)
65%
d)
10%
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Avantika Nambiar answered |
Probability of Having a Girl Child in Sixth Pregnancy
Given that the first five progenies are boys, the probability of having a girl child in the sixth pregnancy can be calculated using the following steps:
Step 1: Determine the probability of having a girl child in one pregnancy.
The probability of having a girl child in one pregnancy is 50%, as there are only two possible outcomes: either a girl or a boy.
Step 2: Determine the probability of having five boys in a row.
The probability of having five boys in a row is (1/2)^5 = 1/32, as the probability of having a boy in one pregnancy is 1/2.
Step 3: Determine the probability of having at least one girl in the sixth pregnancy.
The probability of having at least one girl in the sixth pregnancy is the complement of having six boys in a row, which is 1 - (1/2)^6 = 1 - 1/64 = 63/64.
Step 4: Determine the probability of having a girl child in the sixth pregnancy given that the first five progenies are boys.
The probability of having a girl child in the sixth pregnancy given that the first five progenies are boys is the product of the probability of having five boys in a row and the probability of having at least one girl in the sixth pregnancy, which is:
(1/32) x (63/64) = 63/2048
Therefore, the probability of having a girl child in the sixth pregnancy if the first five progenies are boys is 50%.
Given that the first five progenies are boys, the probability of having a girl child in the sixth pregnancy can be calculated using the following steps:
Step 1: Determine the probability of having a girl child in one pregnancy.
The probability of having a girl child in one pregnancy is 50%, as there are only two possible outcomes: either a girl or a boy.
Step 2: Determine the probability of having five boys in a row.
The probability of having five boys in a row is (1/2)^5 = 1/32, as the probability of having a boy in one pregnancy is 1/2.
Step 3: Determine the probability of having at least one girl in the sixth pregnancy.
The probability of having at least one girl in the sixth pregnancy is the complement of having six boys in a row, which is 1 - (1/2)^6 = 1 - 1/64 = 63/64.
Step 4: Determine the probability of having a girl child in the sixth pregnancy given that the first five progenies are boys.
The probability of having a girl child in the sixth pregnancy given that the first five progenies are boys is the product of the probability of having five boys in a row and the probability of having at least one girl in the sixth pregnancy, which is:
(1/32) x (63/64) = 63/2048
Therefore, the probability of having a girl child in the sixth pregnancy if the first five progenies are boys is 50%.
A color-blind man marries a woman with no family history of color-blindness. What is the likelihood that they have a color-blind daughter?- a)0%
- b)25%
- c)50%
- d)100%
Correct answer is option 'A'. Can you explain this answer?
A color-blind man marries a woman with no family history of color-blindness. What is the likelihood that they have a color-blind daughter?
a)
0%
b)
25%
c)
50%
d)
100%
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Orion Classes answered |
The correct answer is A. 0%. Color blindness is a sex-linked recessive trait that is carried on the X chromosome. In this scenario, since the man is color-blind, he must have the recessive allele for color blindness (XcY) on his X chromosome. The woman, with no family history of color-blindness, is most likely homozygous for the dominant allele (XCXC) on her X chromosome.
When they have children, all the daughters will receive one X chromosome from the father (Xc) and one X chromosome from the mother (XC). Since the mother's X chromosome does not carry the color-blind allele, none of the daughters will be color-blind. The sons, on the other hand, have a 50% chance of inheriting the X chromosome with the color-blind allele from the father and being color-blind themselves.
The results of a linkage analysis of genes A, B, C, and D have just come in from the lab. In what order are the alleles found on the chromosome?
- a)ABCD
- b)DCAB
- c)CDAB
- d)ACDB
Correct answer is option 'B'. Can you explain this answer?
The results of a linkage analysis of genes A, B, C, and D have just come in from the lab. In what order are the alleles found on the chromosome?
a)
ABCD
b)
DCAB
c)
CDAB
d)
ACDB
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Orion Classes answered |
Based on the given recombination frequencies, we can determine the order of the alleles on the chromosome. The pairs with the lowest recombination frequencies are likely to be the closest together on the chromosome. Let's analyze the given recombination frequencies:
A/B: 3.0%
A/C: 5.0%
B/C: 8.0%
A/D: 8.0%
C/D: 3.0%
A/C: 5.0%
B/C: 8.0%
A/D: 8.0%
C/D: 3.0%
From these frequencies, we can conclude that the A and B alleles have the lowest recombination frequency, indicating that they are closest together. Similarly, the C and D alleles also have the lowest recombination frequency, suggesting that they are also closely linked.
Now let's consider the order of the alleles. Since A and B are closest together, they should be adjacent to each other on the chromosome. Similarly, C and D should be adjacent to each other.
Based on this information, the most likely order of the alleles on the chromosome is:
B - A - C - D
Therefore, option B (DCAB) is the most accurate representation of the order of alleles on the chromosome.
A researcher was doing test crosses on mice, but forgot which mice he had bred together. When the litter was born, every mouse had black eyes, and half had brown fur. What was the genotype of the parent mice?
R = red fur; r = brown fur
B = black eyes; b = brown eyes- a)RrBb x rrBB
- b)RrBB x Rrbb
- c)rrBb x RRBB
- d)RrBb x RrBb
Correct answer is option 'A'. Can you explain this answer?
A researcher was doing test crosses on mice, but forgot which mice he had bred together. When the litter was born, every mouse had black eyes, and half had brown fur. What was the genotype of the parent mice?
R = red fur; r = brown fur
B = black eyes; b = brown eyes
R = red fur; r = brown fur
B = black eyes; b = brown eyes
a)
RrBb x rrBB
b)
RrBB x Rrbb
c)
rrBb x RRBB
d)
RrBb x RrBb
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Orion Classes answered |
To determine the genotype of the parent mice, we can use the observed phenotypes of the offspring.
Given that all the offspring have black eyes, we can infer that the parent mice must have at least one dominant allele for eye color, which is B. This rules out options C and D.
Half of the offspring also have brown fur, which suggests that the parent mice must be heterozygous for fur color. This means that they must have one dominant allele (R) and one recessive allele (r) for fur color.
Considering these observations, the most likely genotype of the parent mice is:
RrBb x rrBB
Therefore, option A is the most probable genotype of the parent mice based on the given information.
A nonsense mutation is one that:- a)Adds an additional codon to an RNA transcript
- b)Deletes segments of RNA
- c)Changes an amino acid from one to another
- d)Creates a premature stop codon
Correct answer is option 'D'. Can you explain this answer?
A nonsense mutation is one that:
a)
Adds an additional codon to an RNA transcript
b)
Deletes segments of RNA
c)
Changes an amino acid from one to another
d)
Creates a premature stop codon
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Orion Classes answered |
A nonsense mutation is a type of genetic mutation that introduces a premature stop codon in the DNA or mRNA sequence. A stop codon is a specific sequence of three nucleotides (UAA, UAG, or UGA) that signals the termination of protein synthesis during translation. When a nonsense mutation occurs, it results in the substitution of a normal codon (which codes for an amino acid) with a premature stop codon. This premature stop codon prematurely terminates the translation process, leading to the production of a truncated or non-functional protein. Therefore, option D is the correct answer.
What is the benefit of anti-oxidant compounds?- a)Catalyze production of free-radicals in the cell
- b)Counteract the actions of damaging reactive oxygen species
- c)Reverse existing mutations resulting from reactive oxygen species
- d)Diminish direct damage of O2 on red blood cells
Correct answer is option 'B'. Can you explain this answer?
What is the benefit of anti-oxidant compounds?
a)
Catalyze production of free-radicals in the cell
b)
Counteract the actions of damaging reactive oxygen species
c)
Reverse existing mutations resulting from reactive oxygen species
d)
Diminish direct damage of O2 on red blood cells
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Orion Classes answered |
Antioxidant compounds play a crucial role in counteracting the actions of damaging reactive oxygen species (ROS) in the body. Reactive oxygen species are highly reactive molecules that can cause oxidative damage to cells, DNA, proteins, and lipids. They are produced as byproducts of normal cellular metabolism and can also be generated due to external factors such as exposure to pollutants, radiation, or certain chemicals.
Antioxidants work by neutralizing or scavenging reactive oxygen species, reducing their harmful effects on cells. They donate electrons or hydrogen atoms to reactive oxygen species, effectively stabilizing them and preventing them from causing damage to cellular components. By doing so, antioxidants help protect cells from oxidative stress and maintain their normal function.
Nitric oxide (NO) is an important cardiovascular signaling molecule. It has also been implicated in DNA mutations in bacteria and in human cells, though these mutations are not always associated with cancer formation. Therefore, NO would be an example of an:- a)Exogenous carcinogen
- b)Exogenous mutagen
- c)Endogenous carcinogen
- d)Endogenous mutagen
Correct answer is option 'D'. Can you explain this answer?
Nitric oxide (NO) is an important cardiovascular signaling molecule. It has also been implicated in DNA mutations in bacteria and in human cells, though these mutations are not always associated with cancer formation. Therefore, NO would be an example of an:
a)
Exogenous carcinogen
b)
Exogenous mutagen
c)
Endogenous carcinogen
d)
Endogenous mutagen
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Orion Classes answered |
Endogenous mutagens are substances or factors that naturally occur within an organism and have the potential to cause mutations in DNA. Nitric oxide (NO) is produced endogenously in the body and can act as a mutagen, leading to DNA mutations in both bacteria and human cells. While DNA mutations can be associated with cancer formation, in this case, the statement mentions that the mutations caused by NO are not always linked to cancer. Therefore, NO would be considered an endogenous mutagen, as it is a naturally occurring molecule that can induce genetic changes.
Which of the following is true of large-scale deletions?- a)Enhance silencing of important oncogenes due to altered methylation
- b)Less likely to be fatal than nucleotide-level mutations
- c)Usually involve changes to DNA as well as to epigenetic mechanisms
- d)More likely to result in frameshift mutations than small deletions
Correct answer is option 'C'. Can you explain this answer?
Which of the following is true of large-scale deletions?
a)
Enhance silencing of important oncogenes due to altered methylation
b)
Less likely to be fatal than nucleotide-level mutations
c)
Usually involve changes to DNA as well as to epigenetic mechanisms
d)
More likely to result in frameshift mutations than small deletions
|
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Orion Classes answered |
Large-scale deletions can involve not only the removal of DNA sequences but also alterations in the surrounding chromatin structure and epigenetic modifications. These changes can affect the regulation of nearby genes and alter the overall chromatin landscape. Therefore, option C is the accurate statement regarding large-scale deletions.
Which of the following statements about synaptonemal complexes is not true?- a)They form between sister chromatids
- b)They are made up of functional RNA and protein
- c)They form during synapsis
- d)They act as a support structure
Correct answer is option 'B'. Can you explain this answer?
Which of the following statements about synaptonemal complexes is not true?
a)
They form between sister chromatids
b)
They are made up of functional RNA and protein
c)
They form during synapsis
d)
They act as a support structure
|
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Orion Classes answered |
Synaptonemal complexes are primarily composed of proteins and not functional RNA. The proteins in the synaptonemal complex play a crucial role in facilitating the pairing and alignment of homologous chromosomes during meiosis. RNA molecules are involved in other cellular processes but are not a major component of synaptonemal complexes.
A set of homologous chromosomes undergoes genetic recombination to create the following results:
Q. Which of the following is the mostly likely recombination event?- a)2 strand single crossover
- b)2 strand triple crossover
- c)3 strand single crossover
- d)
3 strand double crossover
Correct answer is option 'D'. Can you explain this answer?
A set of homologous chromosomes undergoes genetic recombination to create the following results:
Q. Which of the following is the mostly likely recombination event?
a)
2 strand single crossover
b)
2 strand triple crossover
c)
3 strand single crossover
d)
3 strand double crossover
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Orion Classes answered |
A single, double, or triple crossover refers to the number of crossover events.
Only two strands are involved in a crossover at a time.
As we can see in the figure, at least 3 strands are involved in the crossover events, meaning that most likely a 3 strand double crossover event took place.
Only two strands are involved in a crossover at a time.
As we can see in the figure, at least 3 strands are involved in the crossover events, meaning that most likely a 3 strand double crossover event took place.
Which type of mutation results in the sickle-cell disease phenotype?- a)Non-conservative missense mutation
- b)Conservative mutation
- c)Frameshift mutation
- d)Codon deletion
Correct answer is option 'A'. Can you explain this answer?
Which type of mutation results in the sickle-cell disease phenotype?
a)
Non-conservative missense mutation
b)
Conservative mutation
c)
Frameshift mutation
d)
Codon deletion
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|
Orion Classes answered |
Sickle-cell disease is caused by a specific point mutation in the hemoglobin gene, resulting in a non-conservative missense mutation. The mutation involves a substitution of a single nucleotide, leading to a change in the amino acid sequence of the hemoglobin protein. In sickle-cell disease, a glutamate amino acid is replaced by a valine amino acid at a specific position in the hemoglobin protein. This change in amino acid alters the structure and function of the hemoglobin molecule, leading to the characteristic sickle-shaped red blood cells and the associated symptoms of the disease. Therefore, option A is the correct answer.
Which of the following represents a transition?- a)A → T
- b)G → A
- c)G → C
- d)T → A
Correct answer is option 'B'. Can you explain this answer?
Which of the following represents a transition?
a)
A → T
b)
G → A
c)
G → C
d)
T → A
|
|
Orion Classes answered |
A transition is a type of point mutation where a purine base (adenine or guanine) is replaced by another purine base, or a pyrimidine base (thymine or cytosine) is replaced by another pyrimidine base, within a DNA molecule.
In option B, the substitution of guanine (G) with adenine (A) represents a transition because both bases are purines. The substitution does not change the category of the base.
Option A represents a transversion, as it involves the substitution of a purine (adenine) with a pyrimidine (thymine). Option C also represents a transversion, as it involves the substitution of a purine (guanine) with another purine (cytosine). Option D represents a transversion, as it involves the substitution of a pyrimidine (thymine) with a purine (adenine).
Therefore, the correct answer is B. G → A, which represents a transition.
In sickle-cell disease, a glutamate →right arrow valine substitution results in formation of HbS molecules, which:- a)Aggregate abnormally and cannot adequately carry O2
- b)Have abnormally high-affinity binding for O2
- c)Stabilize the wall of the red blood cell against oxidative damage
- d)Cause experience high levels of repulsion between neighboring HbS molecules
Correct answer is option 'A'. Can you explain this answer?
In sickle-cell disease, a glutamate →right arrow valine substitution results in formation of HbS molecules, which:
a)
Aggregate abnormally and cannot adequately carry O2
b)
Have abnormally high-affinity binding for O2
c)
Stabilize the wall of the red blood cell against oxidative damage
d)
Cause experience high levels of repulsion between neighboring HbS molecules
|
|
Orion Classes answered |
In sickle-cell disease, the substitution of glutamate with valine in the hemoglobin protein results in the formation of abnormal hemoglobin molecules called HbS. These HbS molecules have a tendency to aggregate and form long fibers when deoxygenated. This aggregation causes the red blood cells to assume a sickle shape, leading to various complications. The abnormal aggregation interferes with the normal function of hemoglobin, reducing its ability to adequately carry oxygen, resulting in oxygen deprivation in tissues and organs. Therefore, option A is the correct answer.
Which of the following population’s coat/fur/feather color gene is most likely to be in Hardy-Weinberg equilibrium?- a)A pack of wolves in a zoo
- b)A flock of moths that must blend in with their environment to survive
- c)Lab rats being bred by scientists
- d)A flock of seagulls that feeds on one type of fish
Correct answer is option 'D'. Can you explain this answer?
Which of the following population’s coat/fur/feather color gene is most likely to be in Hardy-Weinberg equilibrium?
a)
A pack of wolves in a zoo
b)
A flock of moths that must blend in with their environment to survive
c)
Lab rats being bred by scientists
d)
A flock of seagulls that feeds on one type of fish
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Orion Classes answered |
"A flock of seagulls that feeds on one type of fish," is the most likely population to be in Hardy-Weinberg equilibrium.
In the Hardy-Weinberg equilibrium, certain conditions must be met, including random mating, no migration, no mutations, no natural selection, and a large population size. In the given scenario, the flock of seagulls that feeds on one type of fish is more likely to meet these conditions.
When a population feeds on a single type of fish, it reduces the potential for genetic variations due to different food sources. This can contribute to a more stable gene pool and reduce the likelihood of natural selection affecting the coat/fur/feather color gene frequencies. As long as the population meets the other conditions of the Hardy-Weinberg equilibrium, such as random mating and no migration or mutations, the coat/fur/feather color gene in the seagull population is more likely to be in Hardy-Weinberg equilibrium.
A silent mutation is highly unlikely to affect protein because:- a)The silent mutation does not cause a frameshift
- b)The dominant allele can compensate for the silent mutation
- c)The silent mutation substitutes the same type of amino acid
- d)Multiple codons can code for the same amino acid
Correct answer is option 'D'. Can you explain this answer?
A silent mutation is highly unlikely to affect protein because:
a)
The silent mutation does not cause a frameshift
b)
The dominant allele can compensate for the silent mutation
c)
The silent mutation substitutes the same type of amino acid
d)
Multiple codons can code for the same amino acid
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Orion Classes answered |
A silent mutation is a type of genetic mutation that occurs in the DNA sequence but does not result in a change in the amino acid sequence of the protein. This is because the genetic code is redundant, meaning that multiple codons can code for the same amino acid. For example, there are multiple codons that code for the amino acid alanine (e.g., GCU, GCC, GCA, GCG). If a silent mutation occurs and changes one of these codons to another codon that still codes for alanine, there will be no change in the resulting protein. Since the same amino acid is incorporated into the protein, its structure and function are unaffected. Therefore, option D is the correct answer.
What kind of sex-determination system is present in honey bees?- a)Haplodiploid
- b)Haploid
- c)Diploid
- d)XY type
Correct answer is option 'A'. Can you explain this answer?
What kind of sex-determination system is present in honey bees?
a)
Haplodiploid
b)
Haploid
c)
Diploid
d)
XY type
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Top Rankers answered |
- Honey bees exhibit a haplodiploid type of sex-determination system.
- This type of system has special characteristic features like the males produce sperms by mitosis.
- The male individuals do not have a father and thus cannot have sons, but can have a grandfather and a grandson.
What of the following provides the best evidence that DNA is the genetic material?- a)Biomolecular composition of chromosomes
- b)Transformation using heat-inactivated bacteria
- c)Presence of DNA in all cells
- d)Mechanism of semi-conservative DNA replication
Correct answer is option 'B'. Can you explain this answer?
What of the following provides the best evidence that DNA is the genetic material?
a)
Biomolecular composition of chromosomes
b)
Transformation using heat-inactivated bacteria
c)
Presence of DNA in all cells
d)
Mechanism of semi-conservative DNA replication
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Orion Classes answered |
The experiment conducted by Avery, MacLeod, and McCarty in 1944 demonstrated that when heat-inactivated bacteria containing DNA were mixed with live bacteria of a different strain, the live bacteria were transformed and acquired the genetic traits of the heat-inactivated bacteria. This transformation only occurred when DNA was present, indicating that DNA carries the genetic information.
This experiment provided strong evidence that DNA, rather than proteins or other molecules, is the genetic material responsible for transmitting hereditary information from one generation to the next. It showed that the genetic traits could be transferred through the transfer of DNA, supporting the idea that DNA is the carrier of genetic information.
Many people have DNA mutations that go unnoticed. What type of mutation is most likely to have no effect on phenotype?- a)Missense
- b)Deletion
- c)Frameshift
- d)Chromosomal
Correct answer is option 'A'. Can you explain this answer?
Many people have DNA mutations that go unnoticed. What type of mutation is most likely to have no effect on phenotype?
a)
Missense
b)
Deletion
c)
Frameshift
d)
Chromosomal
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Orion Classes answered |
A missense mutation is a type of DNA mutation that results in a change in a single nucleotide, leading to the substitution of one amino acid for another in the protein sequence. In some cases, this change may not significantly affect the structure or function of the protein. The resulting protein may still be able to carry out its normal role in the cell, and therefore, the mutation may have no noticeable effect on the phenotype of the individual.
It's important to note that the impact of a missense mutation on phenotype can vary depending on the specific mutation, the location of the amino acid change within the protein, and the function of the protein itself. In some cases, a missense mutation may lead to a mild or subtle change in phenotype, while in other cases, it may have more severe consequences. However, compared to other types of mutations such as deletions, frameshift mutations, or chromosomal abnormalities, missense mutations are generally more likely to have no effect on the phenotype.
Intercalation of ethidium bromide into DNA results in:- a)Constitutive expression of oncogenes
- b)Displacement of RNA polymerase
- c)Deformation of the DNA molecule
- d)Missense mutations
Correct answer is option 'C'. Can you explain this answer?
Intercalation of ethidium bromide into DNA results in:
a)
Constitutive expression of oncogenes
b)
Displacement of RNA polymerase
c)
Deformation of the DNA molecule
d)
Missense mutations
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Orion Classes answered |
Intercalation of ethidium bromide into DNA refers to the insertion of ethidium bromide molecules between the base pairs of DNA. This intercalation causes the DNA molecule to deform or undergo structural changes. Ethidium bromide is a fluorescent dye commonly used in molecular biology laboratories to visualize DNA in gel electrophoresis.
It is important to note that intercalation of ethidium bromide into DNA does not directly lead to constitutive expression of oncogenes, displacement of RNA polymerase, or missense mutations. Its primary effect is the distortion of the DNA helix, which can affect various processes involving DNA, such as DNA replication, transcription, and DNA-protein interactions.
Chapter doubts & questions for Meiosis and Genetic Variability (BIO) - MCAT Biological and Biochemical Foundations 2025 is part of MCAT exam preparation. The chapters have been prepared according to the MCAT exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for MCAT 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
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