During synapses, chromatids in homologous pairs of chromosomes often twist around each other, break, exchange segments, and rejoin. This process usually contributes to:
A. the production of identical twins.
B. increased variability in offspring.
C. the formation of polyploid offspring.
D. nondisjunction of homologous chromosomes.
E. mutation of the genes.
The concept described in the question is crossing-over. It is one way that increases variety in offspring. It occurs during meiosis when the replicated homologous chromosomes are in close contact with each other during synapses.