If a chiasma forms between the loci of genes A and B in 20% of the tetrads of an individual - Biology - Principles of Inheritance and Variation

Question

If a chiasma forms between the loci of genes A and B in 20% of the
tetrads of an individual of genotype AB/ab, the percentage of
gametes expected to be Ab is: (a) 5 (b) 10 (c) 20 (d) 40

Saurabh Bajpai · Accepted Answer

Let the number of chromosome tetrads of chromosomes with gene loci
containing A and B be 100 i' e 100 cells are undergoing meiosis at
a time As 20 % of the tetrads during meiosis form chiasma that
means 20 of the 100 chromosome tetrads undergo recombination These
20 recombined tetrads will be divided in 40 cells during
cytokinesis as dyads Thus, a total of 40 gametes will be formed
with Ab combination of genes and 40 gametes will be formed with aB
combination of genes

If a chiasma forms between the loci of genes A and B in 20% of the tetrads of an individual of genotype AB/ab, the percentage of gametes expected to be Ab is: (a) 5 (b) 10 (c) 20 (d) 40