Genetic Variation Definition, Causes, and Examples

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

Definition

In genetic variation, the genetic makeup of organisms within a population change. Genes are inherited segments of DNA that contain codes for the production of proteins. Genes exists in alternate versions, or alleles that determine distinct traits that can be passed on from parents to offspring. 

Genetic variation is important to the processes of natural selection and biological evolution. 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 genetic variations are more favorable or better suited for survival. As organisms with these environmentally selected genes survive and reproduce, more favorable traits are passed on to the population as a whole.

Key Takeaways: Genetic Variation

  • Genetic variation refers to differences in the genetic makeup of individuals in a population.
  • Genetic variation is necessary in natural selection. In natural selection, organisms with environmentally selected traits are better able to adapt to the environment and pass on their genes.
  • Major causes of variation include mutations, gene flow, and sexual reproduction.
  • DNA mutation causes genetic variation by altering the genes of individuals in a population.
  • Gene flow leads to genetic variation as new individuals with different gene combinations migrate into a population.
  • Sexual reproduction promotes variable gene combinations in a population leading to genetic variation.
  • Examples of genetic variation include eye color, blood type, camouflage in animals, and leaf modification in plants.

Genetic Variation Causes

Point Mutation
Computer graphic illustration depicting a point mutation. A point mutation is a genetic mutation where a single nucleotide base is changed.  Alfred Pasieka/Science Photo Library/Getty Images

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 confer neither an advantage or disadvantage. Mutations lead to genetic variation by altering genes and alleles in a population. They may impact an individual gene or an entire chromosome. Although mutations change an organism's genotype (genetic makeup), they may not necessarily change an organism's phenotype.
  • 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. Gene frequencies may also be altered by emigration of organisms out of a population. Immigration of new organisms into a population may help organisms better adapt to changing environmental conditions. Migration of organisms out of a population could result in a lack of genetic diversity.
  • 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

Albino Squirrel
A true albino squirrel photographed eating a nut in Companies Garden in Cape Town, Western Cape Province, South Africa.  David G Richardson/Getty Images

Favorable genetic traits in a population are determined by the environment. Organisms that are better able to adapt to their environment survive to pass on their genes and favorable traits. Sexual selection is commonly seen in nature as animals tend to select mates that have traits that are favorable. As females mate more often with males considered to have more favorable traits, these genes occur more often in a population over time.

A person's skin color, hair color, dimples, freckles, and blood type are all examples of genetic variations that can occur in a human 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 albinism, 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.