Which two genes are most likely to be affected by a crossing over event?

A. a pair of genes located adjacent to another on a chromosome
B. a pair of genes separated by a third gene on a chromosome
C. a pair of genes located at opposite ends of a chromosome
D. a pair of genes located on different chromosomes

Cold case files recently began re-investigating an old murder case. the murder took place in the park; a young man, james, was hit over the head with a brick and killed. police suspected the jealous former boyfriend of james' wife, karen. whoever killed james may have washed their hands in a near-by bird bath as detectives found blood in the bird bath. since the murder took place before dna fingerprinting was available, the suspected killer, ronnie, went free. detectives are now reviewing the blood evidence using dna fingerprinting. based on the dna fingerprints of all possible suspects, who is james' killer?