Genetic+Variation+in+a+Population

Genetic variation is preserved in a population by sexual reproduction. Every gamete or sex cell that is reproduced is genetically different from each other. This happens because of crossing-over in the first phase of meiosis. In the first phase of meiosis the homologous pairs of chromosomes swap genes before the cell divides. All of these things lead to genetic diversity.

The picture below is a gamete.



http://www.biologyreference.com/Ph-Po/Population-Genetics.html