Principles of Inheritance and Variation — Page 16 | NEET Biology

Q151

Haemophilia is more common in males because it is a

A Recessive character carried by Y chromosome

B Dominant character carried by X

C Dominant trait carried by X

D Recessive trait carried by X chromosome

Correct Answer

Option D

Solution

(d) Haemophilia is X-linked recessive; hemizygous males express the recessive allele.

Q152

Which one is a hereditary disease?

A Cataract

B Leprosy

C Blindness

D Phenylketonuria

Correct Answer

Option D

Solution

(d) Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism.

Q153

A colour blind girl is rare because she will be born only when

A her mother and maternal grandfather were colour blind

B her father and maternal grandfather were colour blind

C her mother is colour blind and father has normal vision

D parents have normal vision but grandparents were colour blind

Correct Answer

Option B

Solution

(b) A colour blind girl needs X^c X^c: X^c from father (colour blind) and X^c from mother (carrier, whose father was colour blind).

Q154

Multiple alleles control inheritance of

A phenylketonuria

B colour blindness

C sickle cell anaemia

D blood groups

Correct Answer

Option D

Solution

(d) ABO blood groups are controlled by three multiple alleles: I^A, I^B, I^O.

Q155

Blue eye colour is recessive to brown eye colour. A brown eyed man whose mother was blue eyed marries a blue-eyed woman. The children shall be

A both blue eyed and brown eyed 1:1

B all brown eyed

C all blue eyed

D blue eyed and brown eyed 3:1

Correct Answer

Option A

Solution

(a) Man is Bb (heterozygous); woman is bb. Cross: Bb × bb = 1 Bb (brown) : 1 bb (blue) = 1:1.

Q156

Down syndrome is due to

A crossing over

B linkage

C sex-linked inheritance

D nondisjunction of chromosomes

Correct Answer

Option D

Solution

(d) Non-disjunction of chromosome 21 during meiosis causes trisomy 21 (Down syndrome).

Q157

In human beings, 45 chromosomes / single X / XO abnormality causes

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.

Q158

Segregation of Mendelian factors occurs during

A anaphase I

B anaphase II

C diplotene

D metaphase I

Correct Answer

Option A

Solution

(a) Homologous chromosomes separate during anaphase I of meiosis.

Q159

Of a normal couple, half the sons are haemophilic while half the daughters are carriers. The gene is located on

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 a carrier (X^H X^h) — half sons haemophilic, half daughters carriers.

Q160

A colour blind mother and normal father would have

A colour blind sons and normal/carrier daughters

B colour blind sons and daughters

C all colour blind

D all normal

Correct Answer

Option A

Solution

(a) Colour blind mother (X^c X^c) × normal father (XY): sons all colour blind; daughters all carriers.