"Suppose a crossover occurs between the homologous chromosomes. At what stage or stages of M phase could alleles D and d segregate?"

The question is incomplete as it does not have the options which are:

A prophase I

B telophase I

C anaphase I

D metaphase I

C anaphase I

Explanation:

In organisms, a trait is determined by the genes which occur in the form of pair of alleles on the chromosomes.

The alleles are located on the homologous chromosomes or on the two separate chromatids at the same position called locus. The allele shows the when these alleles come at the exact complementary position during fertilization.

In the question, during the formation of the gametes, these alleles get separated during the anaphase I stage when the homologous chromosomes separate. Therefore in the given question, the alleles D and d segregate during the anaphase I.

Thus, anaphase I is the correct answer.