Question

Sexual reproduction cannot explain the origin of new alleles in a population. Nonetheless, how can sexual reproduction increase the genetic variation of a population? Which steps in sexual reproduction are responsible for this increase in genetic variation?

Answer 1

Sexual reproduction involves fusion of gemetes from two different individuals and they possess variations in their genetic makeup as well as variation occurs in the fusion of gametes.Steps involved are:-

Crossing over:-Early on in the process of meiosis, homologous chromosomes pair up and exchange parts with each other. This process is called crossing over. Each human cell contains 46 chromosomes in the form of 23 pairs of homologous chromosomes. Half of each pair came from mom and half from dad. Homologous chromosomes have the same genes in the same location, and only pair with each other. Each chromosome in a pair can have the same genes or slightly different forms of the same gene. They line up side-by-side and break off pieces of themselves and trade those pieces with each other. Crossing over is the first way that genes are shuffled in sexual reproduction to produce genetic diversity.

Independent assortment:-

Independent assortment is the process in which each homologous chromosome in a pair goes into a separate gamete. Thus, each gamete has only one copy of each gene and that copy may be a different version of the same gene that is in another gamete.

Gamete fusion:-

The third way that sexual reproduction provides greater genetic diversity than asexual reproduction is through the process of fertilization, or gamete fusion. Gametes contain only half the amount of DNA of a normal cell, so two gametes must fuse to form a new cell that will develop into a new organism. Different individuals may have different versions of the same genes -- which is why people generally look different from each other -- so the gametes from those individuals will have one version of each gene. When two gametes fuse, they form an individual with a unique combination of genes. This is why children look similar to their parents.

Another advantage of sexual reproduction for genetic diversity is that it allows for more fertilization opportunities, which can quickly increase the number of organisms that have new combinations of genes.