Crack the Question: Week 8 (Genetics)

Q.1

Source: ICMR JRF 2020

A cow with red coat is crossed with a bull having white coat. Their offspring produced in F1 generation showed roan coat. This effect is produced due to juxtaposition of small patches of red and white color. What can be assumed about the gene controlling coat color in cattle?

a. the alleles of genes controlling coat color show a perfect dominant recessive relationship

b. the alleles of genes controlling coat color are incompletely dominant

c. the alleles of genes controlling coat color are co-dominant

d. the alleles of genes controlling coat color show epistasis

Statement analysis:

a. Dominant–recessive = only one phenotype visible

b. Incomplete dominance = gives intermediate (mixed) color

d. Epistasis = interaction between different genes, not alleles of same gene

c. The presence of both red and white patches indicates that both alleles are expressed simultaneously without blending, which is characteristic of co-dominance.

Correct answer: c. the alleles of genes controlling coat color are co-dominant

Q.2.

Source: CSIR NET June 2020

Which one of the following DNA markers can be used to distinguish between a homozygote and a heterozygote?

a. RAPD
b. AFLP
c. RFLP
d. ISSR

Statement Analysis:

a. RAPD – Dominant marker; cannot distinguish between homozygous and heterozygous individuals.

b. AFLP – Mostly dominant; band presence/absence doesn’t differentiate genotypes.

d. ISSR – Dominant marker; cannot detect heterozygosity.
c. RFLP is a co-dominant marker that produces distinct banding patterns, allowing clear differentiation between homozygous and heterozygous individuals.