Step 1: During meiosis, homologous chromosomes exchange segments in a process called crossing over, which produces new combinations of alleles.
Step 2: Before the physical breakage and reunion mechanism was confirmed, J. Belling suggested an alternative explanation known as the Copy-Choice hypothesis.
Step 3: According to this hypothesis, during replication a new strand is synthesized by using one homolog as template for part of its length, then switching template to the other homolog, effectively copying a recombinant sequence rather than physically breaking and joining pre-existing strands.
Step 4: Since this whole model was built to account for recombinant genotypes, the correct answer is \[\boxed{\text{crossing over}}\]