How does sexual reproduction creates variety?

Answer 1

Crossing over

Independent assortment

Random fertilization

Mutation

1. Crossing over

Crossing over is the exchange of corresponding segments of non-sister chromatids of homologous chromosomes. During prophase I (of meisosis I), homologous chromosomes synapse to form aggregates called either bivalents (bi = 2, and there are two homologous chromosomes in the aggregate) or tetrads (tetra = 4, and there are 4 chromatids in the aggregate). While the chromosomes are synapsed in prophase I, crossing over occurs. As a result, a chromatid that originally consisted of 100% maternal alleles and a chromatid that originally consisted of 100% paternal alleles become chromatids with a mixture of both maternal and paternal alleles. This shuffles genetic information and increases variation.

2. Independent assortment

In metaphase I (of meiosis I), the tetrads (bivalents) line up at the center of the cell. Which pole the maternal and paternal chromosomes face is a matter of chance; and the direction the maternal and paternal chromosomes face in one tetrad has no bearing on which way the maternal and paternal chromosomes of another tetrad face. Thus, when the homologous chromosomes separate and move to opposite poles, each pole will receive a mix of maternal and paternal chromosomes. This shuffles genetic information and increases variation.

3. Random fertilization

Because of the above processes, male animals can potentially produce millions or hundreds of millions of genetically unique sperm. And, male animals typically release millions of sperm during sex. Which one of the millions of genetically unique sperm happens to end up fertilizing the egg is largely a matter of chance. Thus, except foridentical twins, siblings never have exactly the same genetic information.

4 Mutation takes place during replication of DNA which result in new varieties .