Principles of Inheritance and Variation — Page 8 | NEET Biology

Q71

A tall true breeding pea plant crossed with dwarf; F1 selfed. The resulting genotypes were in the ratio of

A 1:2:1 Tall homozygous:Tall heterozygous:Dwarf

B 1:2:1 Tall heterozygous:Tall homozygous:Dwarf

C 3:1 Tall:Dwarf

D 3:1 Dwarf:Tall

Correct Answer

Option A

Solution

(a) F2 genotypic ratio: 1 TT : 2 Tt : 1 tt.

Q72

Haploids are able to express both recessive and dominant mutations because there is

A many alleles for each gene

B two alleles for each gene

C only one allele for each gene

D only one allele in a gene

Correct Answer

Option C

Solution

(c) Haploids have only one allele per gene, so every allele expresses itself.

Q73

What contributed to the success of Mendel?

A Qualitative analysis of data

B Observation of distinct inherited traits

C His knowledge of biology

D Consideration of one character at one time

Correct Answer

Option D

Solution

(d) Mendel's success was due to studying one character at a time and using statistical analysis.

Q74

A normal green male maize is crossed with albino female. The progeny is albino because

A trait for albinism is dominant

B albinos have biochemicals to destroy plastids from green male

C plastids are inherited from female parent

D green plastids of male must have mutated

Correct Answer

Option C

Solution

(c) Plastids are maternally inherited (cytoplasmic inheritance).

Q75

Diploid chromosome number in humans is

A 46

B 44

C 48

D 42

Correct Answer

Option A

Solution

(a) Humans have 46 chromosomes (23 pairs: 22 autosomes + 1 sex chromosome pair).

Q76

Both husband and wife have normal vision though their fathers were colour blind. The probability of their daughter becoming colour blind is

A 0%

B 25%

C 50%

D 75%

Correct Answer

Option A

Solution

(a) Husband is XY (normal); wife is X^C X (carrier). Their daughters will be XX or X^C X — none colour blind.

Q77

In a genetic cross having recessive epistasis, F2 phenotypic ratio would be

A 9:6:1

B 15:1

C 9:3:4

D 12:3:1

Correct Answer

Option C

Solution

(c) Recessive epistasis (aa masks B): 9 A_B_ : 3 A_bb : 4 aaB_/aabb = 9:3:4.

Q78

Which one of the following is one of the characteristics of a linkage group?

A Genes on the same chromosome

B Genes on different chromosomes that assort independently

C Genes controlling the same character

D Alleles of the same gene

Correct Answer

Option A

Solution

(a) A linkage group consists of all genes located on the same chromosome.

Q79

In pea plants with RRYY and rryy hybridized, which F2 offspring would indicate the man is heterozygous A (blood group A)?

A AB A O B

B O only

C A, B, AB, O

D A, AB, B, O only

Correct Answer

Option C

Solution

(c) A man with IA i (heterozygous A) x IB i woman can produce A, B, AB, O progeny.

Q80

A cell at telophase stage shows no cell plate formation and more chromosomes than other cells. This would result in

A Aneuploidy

B Polyploidy

C Somaclonal variation

D Polyteny

Correct Answer

Option B

Solution

(b) Polyploidy results from failure of cell plate formation (non-disjunction at cell division).