Genetic Variation

Blackbird With Leucism
This blackbird (turdus merula) has a condition called leucism. Leucism is a genetic variation that causes the partial loss of pigmentation. Credit: Japatino/Moment Open/Getty Images

Definition: In genetic variation, the genes of organisms within a population change. Gene alleles determine distinct traits that can be passed on from parents to offspring. Gene variation is important to the process of natural selection. The genetic variations that arise in a population happen by chance, but the process of natural selection does not. Natural selection is the result of the interactions between genetic variations in a population and the environment.

The environment determines which variations are more favorable. More favorable traits are thereby passed on to the population as a whole.

Genetic Variation Causes

Genetic variation occurs mainly through DNA mutation, gene flow (movement of genes from one population to another) and sexual reproduction. Due to the fact that environments are unstable, populations that are genetically variable will be able to adapt to changing situations better than those that do not contain genetic variation.

  • DNA Mutation: A mutation is a change in the DNA sequence. These variations in gene sequences can sometimes be advantageous to an organism. Most mutations that result in genetic variation produce traits that┬áconfer neither an advantage or disadvantage.
  • Gene Flow: Also called gene migration, gene flow introduces new genes into a population as organisms migrate into a new environment. New gene combinations are made possible by the availability of new alleles in the gene pool.
  • Sexual Reproduction: Sexual reproduction promotes genetic variation by producing different gene combinations. Meiosis is the process by which sex cells or gametes are created. Genetic variation occurs as alleles in gametes are separated and randomly united upon fertilization. The genetic recombination of genes also occurs during crossing over or the swapping of gene segments in homologous chromosomes during meiosis.

    Genetic Variation Examples

    A person's skin color, hair color, multi-colored eyes, dimples, and freckles are all examples of genetic variations that can occur in a population. Examples of genetic variation in plants include the modified leaves of carnivorous plants and the development of flowers that resemble insects to lure plant pollinators. Gene variation in plants often occurs as the result of gene flow. Pollen is dispersed from one area to another by the wind or by pollinators over great distances. Examples of genetic variation in animals include cheetahs with stripes, snakes that fly, animals that play dead, and animals that mimic leaves. These variations enable the animals to better adapt to conditions in their environments.