Question

Which of the following shows a linkage group in the coupling phase?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Genes which are located on a single chromosome are arranged linearly. But the arrangement of genes could be in 2 different ways.
If the dominant alleles of both the linked genes are present on one chromosome and their recessive alleles are present on its homologous chromosome, the genes are said to be in coupling state.
If the dominant allele of one gene and the recessive allele of another gene is present on one chromosome and their recessive and dominant counterparts are on the homologous chromosome, the genes are said to be in repulsive state.
From among the given options, in option a, the genes are in coupling state and in option b, the genes are in repulsive state. Option c and d don’t represent either coupling or repulsive state.
So, option a is the correct answer.