Suppose an Individual Is Heterozygous for Two Linked Pairs of Alleles

Multiple Choice

Suppose an individual is heterozygous for two linked pairs of alleles on the same chromosome arm,Ab/aB such that the A locus is closer to the centromere than the B locus.Under what conditions would a crossover in a somatic cell generate a twin spot,i.e. ,two adjacent clones of cells,one clone homozygous for a and the other clone homozygous for b?

A) The crossover would have to occur between the A locus and the centromere and involve two homologous (non-sister) chromatids.
B) The crossover would have to occur between the A locus and the B locus and involve two homologous (non-sister) chromatids.
C) The crossover would have to occur between the B locus and the end of the chromosome locus and involve two homologous (non-sister) chromatids.
D) A double crossover would have to occur,with one crossover between the A locus and the centromere and a second crossover between the A and B loci and both crossovers would have to involve two homologous (non-sister) chromatids.
E) No crossover in a somatic cell could generate a twin spot.