Principles of Inheritance and Variation — Page 17 | NEET Biology

Q161

Genes located on Y-chromosome are called

A mutant genes

B sex-linked genes

C autosomal genes

D holandric genes

Correct Answer

Option D

Solution

(d) Holandric genes are on the Y chromosome and are transmitted only from father to all sons.

Q162

In Drosophila, sex is determined by

A whether the egg is fertilized or develops parthenogenetically

B the ratio of number of X-chromosomes to sets of autosomes

C X and Y chromosomes

D the ratio of pairs of X-chromosomes to pairs of autosomes

Correct Answer

Option B

Solution

(b) Bridges demonstrated Drosophila sex is determined by X:autosome ratio (X/A ratio).

Q163

In human beings, 45 chromosomes with single XO causes Turner syndrome

A Down syndrome

B Klinefelter syndrome

C Turner syndrome

D Edward syndrome

Correct Answer

Option C

Solution

(c) Turner syndrome = 45,X (monosomy X) in females.

Q164

Of normal parents, a male child becoming colour blind is possible only when

A no grandparents had colour blindness

B possible only when all four grandparents had normal vision

C possible only when father's mother was colour blind

D possible only when mother's father was colour blind

Correct Answer

Option D

Solution

(d) Mother's father colour blind → mother is carrier → 50% of sons are colour blind.

Q165

Mr. Kapoor has Bb autosomal gene pair and d allele sex-linked. Proportion of Bd in sperms

A Zero

B 1/2

C 1/4

D 1/8

Correct Answer

Option C

Solution

(c) P(b) = 1/2; P(d) = 1/2 (hemizygous for d on X); P(Bd) = 1/2 × 1/2 = 1/4.

Q166

Of a normal couple, half the sons are haemophilic. The gene is located on one X-chromosome of mother

A X-chromosome of father

B Y-chromosome of father

C one X-chromosome of mother

D both X-chromosomes of mother

Correct Answer

Option C

Solution

(c) Mother is carrier (X^H X^h); half her sons receive X^h and are haemophilic.

Q167

Haploids are preferred over diploids for mutation studies because in haploids

A recessive mutations express immediately

B dominant mutations express immediately

C mutations are readily induced

D tissue culture is easy

Correct Answer

Option A

Solution

(a) In haploids, there is no dominant allele to mask recessive mutations — they express immediately.