Principles of Inheritance and Variation — Page 9 | NEET Biology

Q81

Cross between AaBB and aaBB will form

A 1 AaBB:1 aaBB

B All AaBB

C 3 AaBB:1 aaBB

D 1 AaBB:3 aaBB

Correct Answer

Option A

Solution

(a) AaBB x aaBB gives 1/2 AaBB and 1/2 aaBB.

Q82

In a marriage between male with blood group A and female with blood group B, the progeny had either AB or B blood group. The possible genotype of parents is

A IA i (Male); IB i (Female)

B IA i (Male); IB IB (Female)

C IA IA (Male); IB IB (Female)

D IA IA (Male); IB i (Female)

Correct Answer

Option B

Solution

(b) IA i x IB IB gives IAIB (AB) and IBi (B) offspring only.

Q83

Two crosses between the same pair of genotypes in which the source of gametes is reversed is known as

A reverse cross

B test cross

C reciprocal cross

D dihybrid cross

Correct Answer

Option C

Solution

(c) Reciprocal cross: the same genotypes are crossed but the sexes of the parents are swapped.

Q84

H.J. Muller was awarded Nobel Prize for

A discovery that chemicals can induce gene mutations

B discovery that ionizing radiations can induce gene mutations

C work on gene mapping in Drosophila

D efforts to prevent use of nuclear weapons

Correct Answer

Option B

Solution

(b) H.J. Muller received the Nobel Prize for discovering that ionizing radiation induces gene mutations.

Q85

Sex is determined in human beings

A by ovum

B at time of fertilization

C 40 days after fertilization

D seventh to eighth week when genitals differentiate

Correct Answer

Option B

Solution

(b) Sex of the zygote is determined at fertilization by which sperm (X or Y) fertilizes the egg.

Q86

The polytene chromosomes were discovered for the first time in

A Drosophila

B Chironomus

C Musca nebulo

D Musca domestica

Correct Answer

Option B

Solution

(b) Balbiani (1881) first observed polytene chromosomes in salivary glands of Chironomus.

Q87

Barr body in mammals represents

A all the heterochromatin in female cells

B Y-chromosomes in somatic cells of male

C all heterochromatin in male and female cells

D one of the two X-chromosomes in somatic cells of females

Correct Answer

Option D

Solution

(d) Barr body = the inactivated X chromosome (condensed) in female somatic cells.

Q88

Crossing over that results in genetic recombination in higher organisms occurs between

A sister chromatids of a bivalent

B non-sister chromatids of a bivalent

C two daughter nuclei

D two different bivalents

Correct Answer

Option B

Solution

(b) Crossing over occurs between non-sister chromatids of homologous chromosomes at the chiasma.

Q89

In our society the sex of the child is determined by

A due to some defect in the women

B due to some defect like aspermia in man

C due to the genetic make up of the particular sperm which fertilizes the egg

D due to the genetic make up of the egg

Correct Answer

Option C

Solution

(c) Sex is determined by whether an X-bearing or Y-bearing sperm fertilizes the egg.

Q90

A mother in a family of five daughters is expecting her sixth baby. The chance of its being a son is

A zero

B 25%

C 50%

D 100%

Correct Answer

Option C

Solution

(c) Sex determination is independent each pregnancy; chance of a son is always 50%.