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This process is random and produces unique gametes. During this process sections of homologous chromosomes (bivalents can get entangled and 'swap', in a process called crossing over, to form chiasmata. Meiosis is the division of diploid germline cells in the gonads of an organism to produce haploid gametes for sexual reproduction. Meiosis and random fertilization of gametes

There are also alleles that produce chinchilla and Himalayan coats. This mutation is then passed down into gametes produced by this cell, and if the affected rabbit is bred with a white one there will be a chance of white offspring, even if the brown rabbit breeds true (cannot normally produce white offspring).

Mutations will not be inherited unless the affected cells are gamete producing cells or gametes themselves.įor example, there may be a spontaneous mutation in a germline (gamete producing) cell of an agouti (brown) rabbit that changes the cell's genetic code so that it no longer codes for melanin in fur. Although most mutations are harmful due to their random nature (see the example regarding sickle cell anemia), beneficial mutations may also occur. Mutations may occur for several reasons such as chemical mutagens or exposure to ionizing radiation, or because of errors made when DNA is copied inside a cell at the first stage of mitosis. These abnormal polypeptides can have significant affects on the biochemistry of the organism, for example sickle cell anemia occurs because one base within the gene for beta-hemoglobin is altered. These mutations change the genes within the chromosomes of the organism and can result in new polypeptides being produced. Genetic variation thus occurs due to several factors. Due to this reproductive advantage, the group with the phenotype should produce more viable offspring that over time will increase their percentage in the overall population.

This is based on the current selection pressures in the environment. If members of a population exhibit a specific phenotype which gives them a reproductive advantage over other members of the population not exhibiting that phenotype natural selection will tend to increase the proportion of the population with the favourable phenotype. The prevailing theory in biology is that natural selection is the mechanism by which allele frequency within a population changes over time due to genetic variation and selection pressures.