Question

How can a pair of linked genes be identified?

Answer 1

A pair of linked genes can be identified through a test cross involving their heterozygous condition and observing the offspring phenotypes. Linked genes tend to be inherited together because they are located close to each other on the same chromosome, resulting in fewer recombinant offspring compared to independent assortment. When crossing over occurs, recombinant types appear, but in lesser proportion than parental types. The deviation from the expected 1:1:1:1 ratio in test crosses indicates linkage. For example, in Drosophila, genes for grey body and long wings show complete linkage with no recombinants in progeny. Conversely, incomplete linkage shows recombinants but at frequencies lower than predicted by independent assortment. Thus, linkage is identified by analyzing deviation in offspring ratios from Mendelian expectations and crossover frequencies between genes.