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All questions of Daily Practice & Tests for NEET Exam

In a cross between a pure tall plant with green pod and a pure short plant with yellow pod. How many short plants are produced in F2 generation out of 16?  
  • a)
    1
  • b)
    4
  • c)
    9
  • d)
    3
Correct answer is option 'B'. Can you explain this answer?

Geetika Tiwari answered
In a cross between a pure tall plant with green pod and a pure short plant with yellow pod four short plans are produced in F2 generation as shortness is recessive trait and appear only in homozygous condition.
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Which of the following is an example of co-dominance?
  • a)
    Skin pigmentation in humans
  • b)
    Sex-linkage in humans
  • c)
    Pink flowers of Snapdragon
  • d)
    The ABO blood groups in human
Correct answer is option 'D'. Can you explain this answer?

Krishna Iyer answered
Co-dominance is the phenomenon that deviates from Mendel’s law of inheritance. Both the alleles appear in offspring instead of one as in Mendel’s experiment. ABO blood grouping in human being is example of co-dominance in which both IA and IB appear simultaneously to form AB blood type.

For ABO system of blood groups, allele IA produces N-acetylgalactosamine transferase enzyme which recognises H- antigen present in RBC membrane and adds N-acetylgalactosamine to sugar parts of H antigens to form A antigen.
The allele IB produces galactosyl transferase enzyme which recognized H antigen to form B antigens. Allele i does not produce any sugar or antigen.
IA  and IB are completely dominant over i, in other words antigens A and B are produced. This is because of co-dominance. These antigens determine the type of blood group. Blood group A has antigens B have antigen, AB has both antigens while blood group. Blood group A have antigen A, group B have antigen B, AB has both antigens while blood group O do not carry any antigens.
Thus, six genotypes and four phenotypes are possible.

Dihybrid cross proves the law of________.
  • a)
    Segregation
  • b)
    Purity of gametes
  • c)
    Law of independent assortment
  • d)
    Dominance
Correct answer is option 'C'. Can you explain this answer?

Deepak Joshi answered
Dihybrid cross proves the law of independent assortment. Mendel found that each pair of alleles segregates independently of the other pairs of alleles during gamete formation. This is known as Law of independent assortment. Dihybrid cross - cross between two parents that differ by two pairs of alleles (AABB X aabb). The formation of gametes is an application of this law.

The term ‘Genetics’ was proposed by
  • a)
    Johannsen
  • b)
    Morgan
  • c)
    Mendel
  • d)
    Bateson
Correct answer is option 'D'. Can you explain this answer?

Rahul Bansal answered
Bateson co-discovered genetic linkage with Reginald Punnett and Edith Saunders, and he and Punnett founded the Journal of Genetics in 1910. Bateson also coined the term "epistasis" to describe the genetic interaction of two independent loci.

A human male produces sperms with the genotypes AB, Ab, aB, ab pertaining to two diallelic characters in equal proportions. What is the corresponding genotype of this person?
  • a)
    AABB
  • b)
    AaBb
  • c)
    AABb
  • d)
    AaBB
Correct answer is option 'B'. Can you explain this answer?

Om Desai answered
If the genotype is AaBb the alleles that will be produced will be AB, Ab, aB, ab, since there are two diallelic characters in the genotypes the person must be heterozygous for both genes. AABB is homozygous. So, the correct answer is "AaBb".

A pure tall and a pure dwarf plant were crossed to produce offspring. Offspring were self-crossed. Find out the ratio between true breeding tall to true breeding dwarf.​
  • a)
    3:1
  • b)
    1:1
  • c)
    2:1
  • d)
    1:2:1
Correct answer is option 'B'. Can you explain this answer?

Rajesh Chatterjee answered
As true tall breeding and true dwarf breeding is seen only a single time in F2 generation, and the remaining are hybtid tall...so the ratio becomes 1:2:2:1.But 1:1 is the ratio for only true tall breeding nd true dwarf breeding in F2 generation.

The gene which controls many characters is called
  • a)
    Pleiotropic gene
  • b)
    Co-dominant gene
  • c)
    Multiple gene
  • d)
    Polygene
Correct answer is option 'A'. Can you explain this answer?

Suresh Iyer answered
A single gene may have two or more phenotypic expressions. The multiple phenotypic effect of a single gene is called pleiotropism. Hence the gene associated with this phenomenon is called Pleiotropic gene.

Sickle cell anaemia is:
[2009]
  • a)
    caused by a change in a single base pair of DNA
  • b)
    caused by substitution of glutamic acid by valine in the beta globin chain of haemoglobin
  • c)
    characterized by elongated sickle like RBCs with a nucleus
  • d)
    an autosomal linked dominant trait
Correct answer is option 'B'. Can you explain this answer?

Krish Saha answered
Sickle cell anaemia is caused by a change in a single base pair of DNA. Sickle-cell anaemia is the name of a specific form of sickle-cell disease in which there is homozygosity for the mutation that causes HbS. Sickle-cell disease, or sicklecell anaemia (or drepanocytosis), is a life-long blood disorder characterized by red blood cells that assume an abnormal, rigid, sickle shape. Sickling decreases the cells flexibility and results in a risk of various complications. ‘

 Fruit colour in squash in an example of:          [2014]
  • a)
    Recessive epistasis
  • b)
    Dominant epistasis
  • c)
    Complementary genes
  • d)
    Inhibitory genes 
Correct answer is option 'B'. Can you explain this answer?

Raghav Khanna answered
(b) Epistasis is the phenomenon of suppression of phenotypic expression of gene by a nonallelic gene which shows its own effect. A dominant epistatic allele suppresses the  expression ofa nonallelic gene whether the latter is dominant or recessive. For example, fruit colour of Summer Squash (Cucurbita pepo) is governed by a gene which pruduces yellow colour in dominant state (Y-) and green colour in recessive state (yy). 

In a given plant, red colour (R) of fruits is dominant over white fruit (r); and tallness (T) is dominant over dwarfness (t). If a plant with genotype RrTt is crossed with a plant of genotype rrtt, what will be the percentage of tall plants with red fruits in the next generation?
  • a)
    20%
  • b)
    40%
  • c)
    50%
  • d)
    60%
Correct answer is option 'C'. Can you explain this answer?

Universal Academy answered
According to question, tallness (T) is dominant over dwarfism (t) and red colour (R) is dominant over white (r) fruit colour.
Parent Generation; P1 : RRTt  x  rrtt
F1 generation :

Phenotypic ratio = 1  (tall plant, red fruit)         
: 1 (dwarf plant, red fruit)
; thus, percent of tall plant with red fruit is 50%.

Which of the following is not a Mendelian disorder?
  • a)
    Haemophilia
  • b)
    Turner’s syndrome
  • c)
    Cystic fibrosis
  • d)
    Colour blindness
Correct answer is option 'B'. Can you explain this answer?

Devanshi Mehta answered
All humans have 46 chromosomes, which determine who and what we are genetically. Boys have an X and Y chromosome. Girls have 2 X chromosomes. Turner Syndrome is a chromosomal disorder in girls in which part or all of one of the X-chromosomes is missing.
This loss of genetic material causes 2 primary features: namely, short stature and underdeveloped ovaries causing delayed or absent puberty. It is usually diagnosed when a girl is noted to be very short and a chromosome blood test is obtained. It should also be suspected if a girl has not developed breasts by 13-14 years of age or had her menstrual period by 15-16 years of age.  Effective hormonal treatment is available for both the short stature and to stimulate normal pubertal changes.

Which one of the following conditions in humans. is correctly matched with its chromosomal abnormality/linkage?
[2008]
  • a)
    Klinefelters syndrome-44 autosomes + XXY
  • b)
    Colour blindness - Y-linked
  • c)
    Erythroblastosis foetalis - X-linked
  • d)
    Downs syndrome - 44 autosomes + XO 
Correct answer is option 'A'. Can you explain this answer?

Mahi Shah answered
Klinefelter's syndrome is a genetic disorder affecting men in which an individual gains an extra X chromosome, so that the usual Karyotype of XY is replaced by one of XXY. Symptoms of  Klinefelter's syndrome  named after us physician H.P. Klinefelter, include female characteristics (such as breast enlargement). 

What will be expected blood groups in the off spring when there is a cross between AB blood group mother and heterozygous B blood group father?
  • a)
    25% AB, 25% A, 50%B
  • b)
    50% AB, 25% A, 25%B
  • c)
    25% AB, 50% O, 25%A
  • d)
    25% O, 25% A, 50%B
Correct answer is option 'A'. Can you explain this answer?

Suresh Kumar answered
Given; Mother is with "AB" blood group....i.e. it means the genotypes are 'IAIB' .. For "B" blood group genotypes are:-'IBIB'(homozygous condition);'IBIO'(Heterozygous condition).. In question it is said that Father is with "B" heterozygous blood group...So;the genotypes are 'IBIO' ... When cross is done between Mother with 'IAIB' & father with 'IBIO'.. the possible genotypes of the progeny are :- 'IAIB'(i.e."AB" blood group);'IAIO'(i.e."A" blood group);'IBIB'(i.e."B" blood group);'IBIO'(i.e."B" blood group).. % of "AB" blood group=>1×100/4 =>25% of progeny with "AB" blood group.. % of "A" blood group=>1×100/4 =>25% of progeny with "A" blood group.. % of "B" blood group =>2×100/4 =>50% of progeny with "B" blood group.... Hence;option _'A'_holds true here...

Study the pedigree chart given below: What does it show?
[2009]
  • a)
    Inheritance of a condition like phenylketonuria as an autosomal recessive trait
  • b)
    The pedigree chart is wrong as this is not possible
  • c)
    Inheritance of a recessive sex - linked disease like haemophilia
  • d)
    Inheritance of a sex -linked inborn error of metabolism like phenylketonuria
Correct answer is option 'A'. Can you explain this answer?

Ishani Nambiar answered
The chart shows the inheritance of a condition like phenylketonuria as an autosomal recessive trait. Parents’ needs to be heterozygous as two of their children are known to be sufferer of the disease. It cannot be recessive sex linked inheritance because then the male parent would also be sufferer.

Which of the following statements are correct about Klinefelter’s Syndrome?      (NEET 2023)
A. This disorder was first described by Langdon Down (1866).
B. Such an individual has overall masculine development. However, the feminine developement is also expressed.
C. The affected individual is short statured.
D. Physical, psychomotor and mental development is retarded.
E. Such individuals are sterile.
Choose the correct answer from the options given below:
  • a)
    A and B only
  • b)
    C and D only
  • c)
    B and E only
  • d)
    A and E only
Correct answer is option 'C'. Can you explain this answer?

Top Rankers answered
B. Such an individual has overall masculine development. However, the feminine development is also expressed. People with Klinefelter syndrome are male (XY), but they often have certain physical characteristics that may be typically associated with female development, such as wider hips, less body hair, and sometimes breast tissue development.
E. Such individuals are sterile. Often, individuals with Klinefelter syndrome produce little to no sperm and are therefore usually infertile. However, there are cases where fertility treatments can help some men with Klinefelter syndrome to father children.
For the other options :
A. This disorder was first described by Langdon Down (1866). This is incorrect. Klinefelter's syndrome was first described by Dr. Harry Klinefelter in the 1940s, not by Langdon Down.
C. The affected individual is short statured. This is incorrect. In fact, individuals with Klinefelter's syndrome are often taller than average.
D. Physical, psychomotor and mental development is retarded. This is also incorrect. While individuals with Klinefelter syndrome may have some learning difficulties or delays, particularly with language and speech, it is not accurate or appropriate to say that their physical, psychomotor, and mental development is "retarded". They may face some challenges, but with support they can lead healthy, productive lives.

A man whose father was colour blind marries a woman who had a colour blind mother and normal father. What percentage of male children of this couple will be colour blind?      [2013]
  • a)
    25%
  • b)
    0%
  • c)
    50%
  • d)
    75% 
Correct answer is option 'C'. Can you explain this answer?

Shivani Rane answered
As color blindness is an autosomal recessive genetic disorder, for it is present at X -chromosome. Thus, according to the situation given in the question, a man whose father was color blind (will be, i.e, XY normal) marries a woman whose mother was color blind and father was normal (i.e, this woman will be a carrier) according to the cross given in the first figure.
Thus, when marriage will happen between a normal man and a carrier woman, in that case, the percentage of a male child to be colorblind is 25% (this can be easily observed from the second figure).So, the correct answer is '50%'.
 

Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by      (NEET 2023)
  • a)
    Thomas Hunt Morgan
  • b)
    Sutton and Boveri
  • c)
    Alfred Sturtevant
  • d)
    Henking
Correct answer is option 'C'. Can you explain this answer?

Knowledge Centre answered
  • Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome.
  • Sutton and Boveri proposed chromosomal theory of inheritance.
  • Henking discovered X-chromosome.
  • Thomas Hunt Morgan proved chromosomal theory of inheritance and proposed the concept of linkage.

The test cross is used to determine the________.
  • a)
    Genotype of the plant
  • b)
    Phenotype of the plant
  • c)
    Both a and b
  • d)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Arpita Tiwari answered
The test cross is used to determine the genotype of the plant in which F1 plant is crossed with homozygous recessive plants. If the ratio is 1:1 the plant is homozygous.

A cell at telophase stage is observed by a student in a plant brought from the field. He tells his teacher that this cell is not like other cells at telophase stage. There is no formation of cell plate and thus the cell is containing more number of chromosomes as compared to other dividing cells. This would result in          [2016]
  • a)
    Aneuploidy
  • b)
    Polyploidy
  • c)
    Somaclonal variation
  • d)
    Polyteny 
Correct answer is option 'B'. Can you explain this answer?

Sushant Goyal answered
(b) This phenomenon is known as Polyploidy, wherein the cells contain more than two paired (homologous) sets of chromosomes. Polyploidy is often seen in the case of plants. The major cause of polyploidy is the non - disjunction of sister chromatids during meiotic recombination. This condition is actually useful in development of new crop varieties. 

The phenotypic ratio in the F2 generation of a dihybrid cross is​
  • a)
    1:2:2:4:1:2:1:2:1
  • b)
    9:3:3:1
  • c)
    7:1:1:7
  • d)
    12:3:4
Correct answer is option 'B'. Can you explain this answer?

Neha Sharma answered
Because it produces produced nine plants with round, yellow seeds, three plants with round, green seeds, three plants with wrinkled, yellow seeds and one plant with wrinkled, green seeds.therefore the ratio is 9 : 3 : 3 : 1

Can you explain the answer of this question below:

The phenotypic ratio in the F2 generation of a dihybrid cross is​

  • A:

    1:2:2:4:1:2:1:2:1

  • B:

    9:3:3:1

  • C:

    7:1:1:7

  • D:

    12:3:4

The answer is b.

Ashish Dasgupta answered
Explanation:

In a dihybrid cross, two traits are considered simultaneously. The F1 generation produced after crossing two pure breeding lines will all be heterozygous for both traits.

For example, if two pure breeding plants with yellow round seeds (YYRR) are crossed with plants with green wrinkled seeds (yyrr), the F1 generation will all be heterozygous for both traits (YyRr).

When the F1 generation is crossed with itself or another F1 individual, the resulting F2 generation will exhibit all possible combinations of the two traits.

The phenotypic ratio in the F2 generation of a dihybrid cross is determined by the number of possible combinations of the two traits.

The possible combinations of the two traits can be determined using a Punnett square or the FOIL method.

For example, using the FOIL method:

(YyRr) x (YyRr)
YYRr YyRR YyRr yyRR
YYRr YyRR YyRr yyRR
YyRr yyRR YyRr yyrr
yyRR yyRR yyrr yyrr

In this example, there are 9 individuals with both dominant traits (yellow and round seeds), 3 individuals with one dominant and one recessive trait (yellow and wrinkled seeds, green and round seeds), and 1 individual with both recessive traits (green and wrinkled seeds).

Therefore, the phenotypic ratio in the F2 generation of this dihybrid cross is 9:3:3:1, which is option B.

Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called
  • a)
    Back cross
  • b)
    Dihybrid cross
  • c)
    Reciprocal cross
  • d)
    Test cross
Correct answer is option 'D'. Can you explain this answer?

Ayush Joshi answered
Test cross is the cross of the individuals with its homozygous recessive parent. In other words, we can say that it is a specialized back cross of F1 hybrid with it's homozygous recessive parent in order to determine whether it is homozygous or heterozygous for a character. Reciprocal cross is the cross that could be made either way or independent of the sex of the parents. Dihybrid cross is the cross of the hybrids of F1 generations with either of its parents. 

With green pods as a dominant trait over yellow, which of the following crosses will result in all progeny having yellow pods?
  • a)
    Homozygous green and homozygous yellow
  • b)
    Heterozygous green and heterozygous green
  • c)
    Homozygous yellow and homozygous yellow
  • d)
    Homozygous green and homozygous green
Correct answer is option 'C'. Can you explain this answer?

Anjali Sharma answered
Yellow being recessive will express only when both alleles are present. That occurs only when both parents can contribute an allele encoding for the yellow pod. For all progeny to have yellow pods, both parents have to be homozygous for yellow pods.

The genotype of a plant showing the dominant phenotype can be determined by :
[2010]
  • a)
    test cross
  • b)
    dihybrid cross
  • c)
    pedigree analysis
  • d)
    back cross
Correct answer is option 'A'. Can you explain this answer?

Pankaj Banerjee answered
Test cross is the cross of an individual with an individual having recessive phenotype. It is used to determine the genotype of a plant showing the dominant phenotype, that means to determine whether the individual exhibiting dominating characters are homozygous or heterozygous.

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