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Case Based Questions Test: Principles of Inheritance & Variation - 2 - Grade 12 MCQ


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15 Questions MCQ Test - Case Based Questions Test: Principles of Inheritance & Variation - 2

Case Based Questions Test: Principles of Inheritance & Variation - 2 for Grade 12 2024 is part of Grade 12 preparation. The Case Based Questions Test: Principles of Inheritance & Variation - 2 questions and answers have been prepared according to the Grade 12 exam syllabus.The Case Based Questions Test: Principles of Inheritance & Variation - 2 MCQs are made for Grade 12 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Case Based Questions Test: Principles of Inheritance & Variation - 2 below.
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Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 1
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Direction: Read the following text and answer the following questions on the basis of the same :

Sickle cell anaemia is a genetic disorder where the body produces an abnormal haemoglobin called haemoglobins. Red blood cells are normally flexible and round, but when the haemoglobin is defective, blood cells take on a “sickle” or crescent shape. Sickle cell anaemia is caused by mutations in a gene called HBB.

It is an inherited blood disorder that occurs if both the maternal and paternal copies of the HBB gene are defective. In other words, if an individual receives just one copy of the defective HBB gene, either from mother or father, then the individual has no sickle cell anaemia but has what is called “sickle cell trait”. People with sickle cell trait usually do not have any symptoms or problems but they can pass the mutated gene onto their children. Three inheritance scenarios can lead to a child having sickle cell anaemia :

— Both parents have sickle cell trait

— One parent has sickle cell anaemia and the other has sickle cell trait

— Both parents have sickle cell anaemia

The following statements are drawn as conclusions from the above data (Kenya).

I. Patients with SCD (Sickle Cell Disease) are less likely to be infected with malaria.

II. Patients with SCD (Sickle Cell Disease) are more likely to be infected with malaria.

III. Over the years the percentage of people infected with malaria has been decreasing.

IV. Year 2000 saw the largest percentage difference between malaria patients with and without SCD.

Choose from below the correct alternative.

Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 1
Patients with SCD (Sickle Cell Disease) are less likely to be infected with malaria. Several studies suggested that, in one way or another, sickle hemoglobin might get in the way of the Plasmodium parasite infecting red blood cells, reducing the number of parasites that actually infect the host and thus conferring some protection against the disease year 2000 saw the largest percentage difference between malaria patients with and without SCD.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 2
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Direction: Read the following text and answer the following questions on the basis of the same :

Sickle cell anaemia is a genetic disorder where the body produces an abnormal haemoglobin called haemoglobins. Red blood cells are normally flexible and round, but when the haemoglobin is defective, blood cells take on a “sickle” or crescent shape. Sickle cell anaemia is caused by mutations in a gene called HBB.

It is an inherited blood disorder that occurs if both the maternal and paternal copies of the HBB gene are defective. In other words, if an individual receives just one copy of the defective HBB gene, either from mother or father, then the individual has no sickle cell anaemia but has what is called “sickle cell trait”. People with sickle cell trait usually do not have any symptoms or problems but they can pass the mutated gene onto their children. Three inheritance scenarios can lead to a child having sickle cell anaemia :

— Both parents have sickle cell trait

— One parent has sickle cell anaemia and the other has sickle cell trait

— Both parents have sickle cell anaemia

If both parents have sickle cell trait, then there is _______________of the child having sickle cell anaemia.

Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 2

If both parents have sickle cell trait, then there is a **25% chance** of the child having sickle cell anaemia.

Solution:
When both parents have the sickle cell trait, they can pass on either a normal gene or the mutated gene to their child. The possible combinations are:

1. Normal gene from both parents (25% chance)
2. Mutated gene from one parent and normal gene from the other (50% chance - child becomes a carrier like the parents)
3. Mutated gene from both parents (25% chance - child has sickle cell anaemia)

So, there is a 25% probability that the child will inherit the mutated gene from both parents and, therefore, have sickle cell anaemia.

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Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 3
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Direction: Read the following text and answer the following questions on the basis of the same :

Sickle cell anaemia is a genetic disorder where the body produces an abnormal haemoglobin called haemoglobins. Red blood cells are normally flexible and round, but when the haemoglobin is defective, blood cells take on a “sickle” or crescent shape. Sickle cell anaemia is caused by mutations in a gene called HBB.

It is an inherited blood disorder that occurs if both the maternal and paternal copies of the HBB gene are defective. In other words, if an individual receives just one copy of the defective HBB gene, either from mother or father, then the individual has no sickle cell anaemia but has what is called “sickle cell trait”. People with sickle cell trait usually do not have any symptoms or problems but they can pass the mutated gene onto their children. Three inheritance scenarios can lead to a child having sickle cell anaemia :

— Both parents have sickle cell trait

— One parent has sickle cell anaemia and the other has sickle cell trait

— Both parents have sickle cell anaemia

If one parent has sickle cell anaemia and the other has sickle cell trait, there is __________that their children will have sickle cell anaemia and ___________will have sickle cell trait.

Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 3
If one parent has sickle cell disease and one parent has sickle cell trait, there is a 50% chance that their children will be born with sickle cell disease. It is equally likely that any given child will get two HbA genes and be completely unaffected.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 4
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Direction: Read the following text and answer the following questions on the basis of the same :

Sickle cell anaemia is a genetic disorder where the body produces an abnormal haemoglobin called haemoglobins. Red blood cells are normally flexible and round, but when the haemoglobin is defective, blood cells take on a “sickle” or crescent shape. Sickle cell anaemia is caused by mutations in a gene called HBB.

It is an inherited blood disorder that occurs if both the maternal and paternal copies of the HBB gene are defective. In other words, if an individual receives just one copy of the defective HBB gene, either from mother or father, then the individual has no sickle cell anaemia but has what is called “sickle cell trait”. People with sickle cell trait usually do not have any symptoms or problems but they can pass the mutated gene onto their children. Three inheritance scenarios can lead to a child having sickle cell anaemia :

— Both parents have sickle cell trait

— One parent has sickle cell anaemia and the other has sickle cell trait

— Both parents have sickle cell anaemia

Sickle cell anaemia is a/an ________________ disease.
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 4
Sickle cell anaemia is an autosomal recessive disease, meaning that it only occurs if both the material and paternal copies of the the HBB gene are defective.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 5
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Direction: Read the following text and answer the following questions on the basis of the same :

Sickle cell anaemia is a genetic disorder where the body produces an abnormal haemoglobin called haemoglobins. Red blood cells are normally flexible and round, but when the haemoglobin is defective, blood cells take on a “sickle” or crescent shape. Sickle cell anaemia is caused by mutations in a gene called HBB.

It is an inherited blood disorder that occurs if both the maternal and paternal copies of the HBB gene are defective. In other words, if an individual receives just one copy of the defective HBB gene, either from mother or father, then the individual has no sickle cell anaemia but has what is called “sickle cell trait”. People with sickle cell trait usually do not have any symptoms or problems but they can pass the mutated gene onto their children. Three inheritance scenarios can lead to a child having sickle cell anaemia :

— Both parents have sickle cell trait

— One parent has sickle cell anaemia and the other has sickle cell trait

— Both parents have sickle cell anaemia

If both parents have sickle cell trait, then there is _______________of the child having sickle cell trait.
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 5
If both parents have sickle cell trait, there is a 50% chance with each pregnancy that the baby will have sickle cell trait. A child with sickle cell anemia appears normal at birth.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 6
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Read the following and answer the questions given below:

Turner’s syndrome is an example of monosomy. It is formed by the union of an allosome free egg and a normal ‘X’ containing sperm or a normal egg and an allosome free sperm. The individual has 2n = 45 chromosomes (44 + X0) instead of 46. Such individuals are sterile females who have rudimentary ovaries, under developed breasts, small uterus, short stature, webbed neck and abnormal intelligence. They may not menstruate or ovulate. This disorder can be treated by giving female sex hormone to the women from the age of puberty to make them develop breasts and have menstruation. This makes them feel more normal.

Assertion : Turners syndrome is caused due to absence of any one of the X and Y sex chromosome.

Reason : Individuals suffering from Turner 'syndrome show masculine as well as feminine development.
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 6
Turner’s syndrome occurs due to absence of X chromosome. Individuals having a single X chromosome 22A+XO (45) have female sexual differentiation but ovaries are rudimentary. Other associated phenotypes of this condition are short stature, webbed-neck, broad chest, lack of secondary sexual characteristics and sterility. Thus, any imbalance in the copies of the sex chromosomes may disrupt the genetic information necessary for normal sexual development.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 7
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Read the following and answer the questions given below:

Turner’s syndrome is an example of monosomy. It is formed by the union of an allosome free egg and a normal ‘X’ containing sperm or a normal egg and an allosome free sperm. The individual has 2n = 45 chromosomes (44 + X0) instead of 46. Such individuals are sterile females who have rudimentary ovaries, under developed breasts, small uterus, short stature, webbed neck and abnormal intelligence. They may not menstruate or ovulate. This disorder can be treated by giving female sex hormone to the women from the age of puberty to make them develop breasts and have menstruation. This makes them feel more normal.

Turner’s syndrome is an example of
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 7
Failure of segregation of chromatids during cell division result in the gain or loss of a chromosomes called aneuploidy. For example, Turners syndrome results due to loss of X chromosome in human females.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 8
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Read the following and answer the questions given below:

Turner’s syndrome is an example of monosomy. It is formed by the union of an allosome free egg and a normal ‘X’ containing sperm or a normal egg and an allosome free sperm. The individual has 2n = 45 chromosomes (44 + X0) instead of 46. Such individuals are sterile females who have rudimentary ovaries, under developed breasts, small uterus, short stature, webbed neck and abnormal intelligence. They may not menstruate or ovulate. This disorder can be treated by giving female sex hormone to the women from the age of puberty to make them develop breasts and have menstruation. This makes them feel more normal.

Which of the following statements regarding Turner’s syndrome is incorrect?
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 8
In Turner’s syndrome individual lacks one X chromosome. This situation is known as monosomy.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 9
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Read the following and answer the questions given below:

Turner’s syndrome is an example of monosomy. It is formed by the union of an allosome free egg and a normal ‘X’ containing sperm or a normal egg and an allosome free sperm. The individual has 2n = 45 chromosomes (44 + X0) instead of 46. Such individuals are sterile females who have rudimentary ovaries, under developed breasts, small uterus, short stature, webbed neck and abnormal intelligence. They may not menstruate or ovulate. This disorder can be treated by giving female sex hormone to the women from the age of puberty to make them develop breasts and have menstruation. This makes them feel more normal.

Number ot barr body present in a female with Turners syndrome is
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 9
Barr body is a structure consisting of a condensed X chromosome that is found in nondividing nuclei of female mammals. The presence of Barr body is used to confirm the sex of athletes in sex determination tests. It is named after the Canadian anatomist M.L. Barr, who identified it. The number of Barr bodies is one less than total number of X chromosomes. In Turner’s syndrome genotype is 45 + X0, so, the number of Barr body is 0.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 10
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Read the following and answer the questions given below:

Turner’s syndrome is an example of monosomy. It is formed by the union of an allosome free egg and a normal ‘X’ containing sperm or a normal egg and an allosome free sperm. The individual has 2n = 45 chromosomes (44 + X0) instead of 46. Such individuals are sterile females who have rudimentary ovaries, under developed breasts, small uterus, short stature, webbed neck and abnormal intelligence. They may not menstruate or ovulate. This disorder can be treated by giving female sex hormone to the women from the age of puberty to make them develop breasts and have menstruation. This makes them feel more normal.

Turner’s syndrome is a/an
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 10
Turner's syndrome is a chromosomal disorder that occurs due to absence of one chromosome.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 11
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Read the following and answer the questions given below:

Haemophilia is a sex linked disease which is also known as bleeder’s disease as the patient will continue to bleed even from a minor cut since he or she does not possess the natural phenomenon of blood clotting due to absence of anti-haemophilic globulin or factor VIII and plasma thromboplastin factor IX essential for it. As a result of continuous bleeding the patient may die of blood loss. Colour blindness is another type of sex linked trait in which the eye fails to distinguish red and green colours. Vision is however, not affected and the colour blind can, lead a normal life, reading, writing and driving (distinguishing traffic lights by their position).

Anup is having colourblindness and is married to Soni who is normal. What is the chance that their son will have the disease?
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 11

Colour blindness is a sex-linked recessive disorder, which results in defects in either red or green cone of an eye which ultimately leads to the failure in discriminating between red and green colour. The gene for colour blindness is located on X-chromosome.

If a colourblind man marries a normal women the chances for their son to be colourblind is 0% because son will receive X-chromosome from his mother (who is not colourblind) and Y from the father (as gene of colour blindness is present on X, so Y chromosome is not affected at all). Thus, there is no chance for their son to be affected. Infact their girl child (daughter) will be the carrier of the disease.

Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 12
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Read the following and answer the questions given below:

Haemophilia is a sex linked disease which is also known as bleeder’s disease as the patient will continue to bleed even from a minor cut since he or she does not possess the natural phenomenon of blood clotting due to absence of anti-haemophilic globulin or factor VIII and plasma thromboplastin factor IX essential for it. As a result of continuous bleeding the patient may die of blood loss. Colour blindness is another type of sex linked trait in which the eye fails to distinguish red and green colours. Vision is however, not affected and the colour blind can, lead a normal life, reading, writing and driving (distinguishing traffic lights by their position).

A man whose father was colourblind and mother was normal marries a woman whose father was haemophilic and mother was normal. Which of the following is true for their progenies? [Note: Percentage is from the total number of progenies.]
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 12
When a man whose father was colourblind and mother was normal (i.e., normal man XY) marries a woman whose father was haemophilic and mother was normal (i.e.y carrier haemophilic woman XhX), then 25% male progenies and 25% female progenies carry the gene of haemophilia.

Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 13
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Read the following and answer the questions given below:

Haemophilia is a sex linked disease which is also known as bleeder’s disease as the patient will continue to bleed even from a minor cut since he or she does not possess the natural phenomenon of blood clotting due to absence of anti-haemophilic globulin or factor VIII and plasma thromboplastin factor IX essential for it. As a result of continuous bleeding the patient may die of blood loss. Colour blindness is another type of sex linked trait in which the eye fails to distinguish red and green colours. Vision is however, not affected and the colour blind can, lead a normal life, reading, writing and driving (distinguishing traffic lights by their position).

If a haemophilic man marries a woman whose father was haemophilic and mother was normal then which of the following holds true for their progenies?
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 13
When a haemophilic man (XhY) marries a woman whose father was haemophilic and mother was normal i.e.t carrier woman (XXh), then 50% daughters are carriers and 50% are haemophilic. This can be explained as follows

Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 14
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Read the following and answer the questions given below:

Haemophilia is a sex linked disease which is also known as bleeder’s disease as the patient will continue to bleed even from a minor cut since he or she does not possess the natural phenomenon of blood clotting due to absence of anti-haemophilic globulin or factor VIII and plasma thromboplastin factor IX essential for it. As a result of continuous bleeding the patient may die of blood loss. Colour blindness is another type of sex linked trait in which the eye fails to distinguish red and green colours. Vision is however, not affected and the colour blind can, lead a normal life, reading, writing and driving (distinguishing traffic lights by their position).

Which of the following statements is incorrect regarding haemophilia?
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 14
Haemophilia is sex linked recessive Mendelian disorder.
Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 15
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Directions: In the following questions, a statement of assertion is followed by a statement of reason.

Assertion: In F2 generation of plant Mirabilis jalapa, the pink coloured flowers appear.

Reason: This is observed due epistatic suppression of white colour alleles in one of parental flowers by red colour alleles.
Detailed Solution for Case Based Questions Test: Principles of Inheritance & Variation - 2 - Question 15
In Mirabilis jalapa (four o’clock) have two types, of flower colour in pure state: red and white. When the two types of plants are crossed, the hybrid or plants of F1 generation produce pink flowers. If the latter are selfed, the plants of F2 generation are of three types-red, pink and white flowered in the ratio of 1 : 2 : 1. Due to incomplete dominance of red (dominant) over white (recessive), the pink colour apparently appears. Thus, pink is differentiated from red and white.
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