Discuss how crossing-over leads to greater variability of phenotype's. give an example to explain your answer.

Crossing over happens in prophase I of meiosis I when the inner chromatids of two synapsed chromosomes trade a section. This gives those two chromatids a different lineup or a different combination of alleles than they had before. So the gametes containing these recombinant chromatids will have the new combination, as will any offspring from those gametes!