FREE NEET Biology Practice MCQ Test: Principles Of Inheritance And Variation Exercise 1 Questions Answers With Detailed Explanations [PDF]

Answer: (b)

Answer: (b)

Answer: (b)

According to Bridges, in Drosophila Y-chromosome is heterochromatic so it is not active in sex determination. In Drosophila sex determination takes place by sex index ratio.

Sex index ratio = ${\text"No. of X-chromosomes"}/{\text"No. of set of autosomes"} = X/A$

Gene of femaleness (Sxl- gene) (Sxl = Sex lethal gene) is located on X-chromosome and gene of maleness is located on autosome. Gene of male fertility is located on Y-chromosome and in Drosophila, Y-chromosome plays additional role in spermatogenesis and development of male reproductive organ, so Y-chromosome is essential for the production of fertile male.

Answer: (d)

Mutation is the sudden inheritable discontinuous variation which appears in an organism due to permanent changes in their genotypes. The term mutation was coined by Hugo de Vries (1901).

Answer: (d)

Answer: (a)

The statement in option (b) is not true. It can be corrected as

The tightly linked genes on chromosomes show 100% parental types and 0% recombinants. Two genes that undergo independent assortment indicated by a recombinant frequency of 50% are on non-homologous chromosomes indicated for apart in a single chromosome. As the distance between two genes increases, crossing over frequency increases. This results in the formation of more recombinant gametes and fewer parental gametes. Rest of the statements are true.

Answer: (b)

Answer: (c)

Colour blindness is a recessive sex-linked trait.

All sons will be colour blind and all daughters will be carriers.

Answer: (c)

Answer: (c)

Answer: (d)

5% of the population are of blood group AB, i.e. 1 out of every 20 individuals is AB.

Answer: (b)

If fertilization takes place between gametes of $Rh^{-}$ female and $Rh^{+}$ male then the resulting foetus' blood is $Rh^{+}$ . The $Rh^{+}$ blood of the foetus stimulates the formation of anti Rh factors in the mother's blood. In second pregnancy (with $Rh^{+}$ foetus), the anti Rh factors of the mother's blood destroy the foetal red blood corpuscles. This is called erythroblastosis foetalis. New born may survive but it is often anaemic. The $Rh^{-}$ child does not suffer.

Answer: (b)

The formula to determine the number of gametes is

$2^n = 2^{(2)} = 4$

Thus, RrYy would produce 4 gametes of the types RY, Ry, rY, ry.

Answer: (a)

Answer: (a)

Husband × Wife = $I^{A} I^{B} × I^{A}i$

Number of genotypes = 4

Number of phenotypes = 3

$I^{A}I^{A}$ and $I^{A}$i = A

$I^{A}I^{B}$ = AB

$I^{B}i$ = B

Answer: (d)

Answer: (a)

Answer: (c)

Down’s syndrome is the chromosomal disorders due to the presence of an additional copy of the chromosome number 21 (trisomy of 21). The affected individual is short statured with small round head, furrowed tongue and partially open mouth and mental development is restarted.

Answer: (a)

Allele for wrinkled shape of seed in garden pea plant is considered to be recessive because the trait (character) associated with the allele is not expressed in heterozygotes.

Answer: (b)