Genetics

The DNA molecule is extremely stable, ensuring that offspring have the same traits and attributes that will enable them to survive as well as their parents. However, a certain amount of genetic variation is necessary if species are to adapt by natural selection to a changing environment. Often, this change in genetic material occurs when chromosome segments from the parents physically exchange segments with each other during the process of meiosis. This is known as cross over or intrinsic recombination.

Genes can also change by mutations on the DNA molecule, which occur when a mutagen alters the chemical or physical makeup of DNA. Mutagens include ultraviolet light and certain chemicals. Genetic mutations in somatic (body) cells result in malfunctioning cells or a mutant organism. These mutations result from a change in the base pairs on the DNA, which can alter cell functions and even give rise to different traits. Somatic cell mutations can result in disfigurement, disease, and other biological problems within an organism. These mutations occur solely within the affected individual.

When mutations occur in the DNA of germ (reproductive) cells, these altered genes can be passed on to the next generation. A germ cell mutation can be harmful or result in an improvement, such as a change in body coloring that acts as camouflage. If the trait improves an individual organism's chances for survival within a particular environment, it is more likely to become a permanent trait of the species because the offspring with this gene would have a greater chance to survive and pass on the trait to succeeding generations.

Mutations are generally classified into two groups, spontaneous mutations and induced mutations. Spontaneous mutations occur naturally from errors in coding during DNA replication. Induced mutations come from outside influences called environmental factors. For example, certain forms of radiation can damage DNA and cause mutations. A common example of this type of mutating agent is the ultraviolet rays of the sun, which can cause skin cancer in some people who are exposed to intense sunlight over long periods of time. Other mutations can occur due to exposure to man-made chemicals. These types of mutations modify or change the chemical structure of base pairs.