Principles of Inheritance and Variation Test

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Principles of Inheritance and Variation Test - 42

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Question 1
1 / -0

In sickle cell anaemia, the glutamic acid is replaced by

A
Proline

B
Alanine

C
Serine

D
Valine

E
Glycine

Solution

Sickle cell anemia is a genetic trait for which the newborns are screened. It is an autosomal recessive disorder which means both copies of the gene in each cell must have mutations to express the symptoms. The homozygous recessive ($${Hb^{s}}$$$${Hb^{s}}$$) are not viable and, hence, the disease is transmitted by heterozygous individuals. Hemoglobin has four protein subunits, two $$\alpha$$-globin and two $$\beta$$-globin. The $${Hb^{b}}$$ gene codes the $$\beta$$-chain. Missense mutation, replacement of A by T at the 17th nucleotide of the $${Hb^{b}}$$ gene changes the codon GAG (glutamic acid) to GTG (which encodes valine). The mutated alllele $$Hb^{s}$$ encodes the abnormal hemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells. The sickle shaped RBC block and damage the vital organs and tissue.
Question 2
1 / -0

In sickle cell anaemia, which of the sequences get changed?

A
$${\alpha}$$-chain

B
$${\beta}$$-chain

C
Both A and B

D
None of the above

Solution

Hemoglobin has four protein subunits, two $$\alpha$$-globin and two $$\beta$$-globin. The Hbb gene codes the beta chain. Missense mutation, replacement of A by T at the 17$$^{th}$$ nucleotide of the Hbb gene changes the codon GAG (glutamic acid) to GTG (which encodes valine).
The mutated alllele Hb$$^s$$ encodes the abnormal hemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells. Function of hemoglobin is to transport oxygen from the lungs to other parts of the body. The sickle shaped RBC block and damage the vital organs and tissue. The hemoglobin $$\beta$$-gene is located on chromosome 11.
Question 3
1 / -0

A family has five girls and no son, the probability of the occurance of son in 6$$^{th}$$ child is

A
1/2

B
1/5

C
1

D
1/4

Solution

The human male has 44+XY chromosomes and the human female has 44+XX chromosomes.
Parent generation : 44+XY x 44+XX
gametes
44+XY----->
44+XX
23+X 23+Y
23+X
44+XX
44+XY
23+X 44+XX 44+XY
F$$_1$$ generation = 1 girl : 1 boy. Hence, the probability of a child being a son is 1/2.
Thus, the correct answer is option A.
Question 4
1 / -0

A family has 9 girls, probability of son at 10$$^{th}$$ birth would be _________.

A
50%

B
100%

C
25%

D
75%

Solution

In humans, both males and females have 23 pairs of chromosomes. Of these 1 pair is called sex chromosomes.
Females have a perfect pair of sex chromosomes, both called X chromosomes. But males have a mismatched pair in which one is a normal-sized X while the other is a short one called Y. So women are XX, while men are XY.
During meiosis, all the gametes produced by females contain only the X chromosome, whereas males produce two kinds of gametes, 1/2 gametes with X-chromosome and 1/2 with Y-chromosome.
Fertilization of the egg with sperm carrying X chromosomes results in a female child (XX).
Fertilization of the egg with sperm carrying Y chromosomes results in a male child (XY).
Thus, each time there is a 50% chance for a child to be a son and 50% to be a daughter; thus, the probability of 10$$^{th}$$ child to be a son is 50%.
So, the correct answer is option A.
Question 5
1 / -0

The diploid number of human chromosomes was corrected from 48 to 46 by

A
Waldeyer

B
Harris and Watkin

C
Tijo and Levan

D
Beadle and Tatum

Solution

Tijo and Levan studied the human embryonic tissue and discovered that there were 46 chromosomes, not 48, using improved techniques for preparing microscope slides and separating chromosomes on it. Thus, the correct answer is option C.
Question 6
1 / -0

In pedigree analysis symbol $$\bigodot$$ is used for

A
Heterozygous for autosomal recessive

B
Affected individuals

C
Death

D
Carrier for sex linked recessive

Solution

In pedigree analysis, a dot in a circle shows the carrier individual for sex linked recessive. Half shaded circle and square are used for heterozygous for autosomal recessive. Full shaded circle and square are used for affected individuals. A square with a diagonal line is used for death. Option D is the correct answer.
Question 7
1 / -0

If a cross is made between two individuals, each having genotype Bb, two offsprings are obtained. Out of these first has dominant trait. What is the probability that the second offspring will exhibit recessive trait?

A
1/4

B
100

C
Zero

D
3/4

Solution

The parent's genotype is "Bb".
Parent generation : Bb x Bb
Gametes :
Bb ---->
Bb
B
b
B BB Bb
b
Bb

bb
F$$_1$$ generation = 3 dominant : 1 recessive. Hence, the probability of a child to be recessive is 1/4. Option A is the correct answer.
Question 8
1 / -0

Sex chromosomes were first studied by

A
Mclung 1902

B
Castle 1903

C
Stevens 1905

D
Correns 1905

Solution

Chromosomes that are involved in sex determination of an organism are called sex chromosomes. The X and Y chromosomes, the sex chromosomes in mammals including human, were first discovered in beetles by Nettie Stevens in 1906. She observed presence of identical looking pairs of each of several chromosomes in female beetles and that of one pair with two morphologically different chromosomes in female beetles. She termed these two chromosomes the X and the Y, and found that female beetles differed from males in containing two X chromosomes. Humans also follow XX-XY mechanism where females are XX and males are XY. Correct option is C.
Castle studies chromosomal basis of sex determination; McClung 1902 reported presence of two types of gametes in male grasshopper (XO); Correns rediscovered Mendel's principals of inheritance while working on incomplete dominance of flower colour in Mirabilis jalapa. Correct option is C.
Question 9
1 / -0

Which one of the following symbols and its representation, used in human pedigree analysis is correct?

A
$$\Box =$$ unaffected female

B
$$\blacklozenge =$$ male affected

C

D
$$\bigcirc =$$ unaffected male

Solution

In pedigree analysis, unaffected male is represented by square and unaffected female by circle. Full shaded diamond represent the affected individuals with unspecified sex. A square and circle is connected with two horizontal lines show the mating between relatives. Option C is the correct answer.
Question 10
1 / -0

Who proposed the chromosomal theory?

A
Bateson and Punnet

B
Mendel

C
Morgan

D
Sutton and Boveri

Solution

The Boveri-Sutton chromosome theory, is a prominent theory of genetics which states that chromosomes are the hereditary units. It elucidates the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors required by Mendel's laws. Chromosomes are the coiled structure composed of DNA which is responsible for the inheritance of characters.

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gametes 44+XY-----> 44+XX	23+X	23+Y
23+X	44+XX	44+XY
23+X	44+XX	44+XY

Gametes : Bb ----> Bb	B	b
B	BB	Bb
b	Bb	bb

Principles of Inheritance and Variation Test - 42

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Principles of Inheritance and Variation Test - 42

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Question 1

Proline

Alanine

Serine

Valine

Glycine

Solution

Question 2

$${\alpha}$$-chain

$${\beta}$$-chain

Both A and B

None of the above

Solution

Question 3

1/2

1/5

1

1/4

Solution

Question 4

50%

100%

25%

75%

Solution

Question 5

Waldeyer

Harris and Watkin

Tijo and Levan

Beadle and Tatum

Solution

Question 6

Heterozygous for autosomal recessive

Affected individuals

Death

Carrier for sex linked recessive

Solution

Question 7

1/4

100

Zero

3/4

Solution

Question 8

Mclung 1902

Castle 1903

Stevens 1905

Correns 1905

Solution

Question 9

$$\Box =$$ unaffected female

$$\blacklozenge =$$ male affected

$$\bigcirc =$$ unaffected male

Solution

Question 10

Bateson and Punnet

Mendel

Morgan

Sutton and Boveri

Solution

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