Question

These homologous chromosomes carry different alleles of the A and B genes. How could crossing over affect the distribution of the four alleles: A, a, B, and b? A. Crossing over would always keep A and B together on the same chromosome, and keep a and b together on the same chromosome. B. Crossing over would always put A and B on different chromosomes, and always put a and b on different chromosomes. C. Crossing over would sometimes, but not always, exchange the positions of A and a, and of B and b, on homologous chromosomes. D. Crossing over would sometimes, but not always, delete one or more of the four alleles from both homologous chromosomes.

Answer 1

Answer:

C. Crossing over would sometimes, but not always, exchange the positions of A and a, and of B and b, on homologous chromosomes.

Explanation:

Crossing over involves the exchange of chromosomal segments (and of course the respective genes on the chromosome segments) between non-sister chromatids in a tetrad during meiosis.

From the attached image, crossing over would sometimes exchange the positions of A and a, and that of B and b on the chromosome. However, this is not the case 100% of the time.

The correct option is C.