Question

One chromosome with alleles A,B,C and the homologous chromosome that contains the alleles a,b,c. If crossing over occurred once during meiosis at a site on the chromosome between the B gene and the C gene, then what alleles could a resulting chromatid contain?

Answer 1

Crossing over between homologous chromosomes can result in recombinant chromatids. After the crossing over between B and C genes, the recombined chromatids could contain either A, B,c or A,b, C. This exchange increases genetic diversity by creating new combinations of alleles.

Step-by-step explanation:

When homologous chromosomes undergo crossing over during meiosis, particularly during prophase I, they can exchange genetic material between non-sister chromatids, which results in recombinant chromosomes. As described in the question, if one chromosome has the alleles A, B, and C and the homologous chromosome has the alleles a,b,c, and crossing over occurs between the B and C genes, the possible chromatids we could see would carry recombined genetic material.

Given that crossing over occurs between B and C genes, the resultant recombinant chromatids might contain the allele combinations: A, B,c or A,b, C, along with the original AB, C, and a, b, c combinations on the non-recombinant chromatids. This process significantly increases genetic diversity in the gametes resulting from meiosis, contributing to genetic variation in offspring.