Consider a pair of homologous chromosomes heterozygous for three genes (e. g. ABC/abc) during prophase I of meiosis. Let the sister chromatids of one homolog be numbered 1 and 2 (ABC); and the sister chromatids of the other homolog be numbered 3 and 4 (abc). Assume a double crossover occurs in this pair of chromosomes that results in chromatids of the genotype Abc, ABC, aBc and abC. If the first crossover (the one between A and B) involves chromatids 1 & 4, which chromatids could be involved in the second crossover?
a. 1 & 2
b. 1 & 3
c. 1 & 4
d. 1 & 3 or 1 & 4 or 2 & 3 or 2 & 4
e. any two of the four chromatids