What is genetic variation? Genetic variation is simply the variation in DNA between individuals or between populations. There are many different sources of genetic variation, such as genetic recombination and mutation. A recent study showed that your genetic makeup is determined by more than just your heritage or race.
Some forms of genetic variation are caused by the actions of thousands of years of natural selection. These include changes caused by the spread of domesticated animals over the landscape and the impact of human intervention, such as the practice of interbreeding between domestic dogs and wolves. Another form of genetic change is caused by the actions of humans, such as using antibiotics and altering their diet. Finally, genetic change can be caused by the actions of Mother Nature, such as the impact of radioactive decay on DNA.
When researchers examine the variations in humans, they look for signatures of prior evolution or mutations. These signatures are usually found in the variation of DNA between unrelated individuals. For instance, if an individual has two parents who both have a variant version of the genetic code, they will still display the same variation, whether or not they share that variation. However, if one parent has a variation and the other does not, the child will also carry the same mutation, even though they are not related. In order to identify whether a person carries a mutation, researchers perform a comparison between two individuals who are of the same breed or ethnic background, but carry no other genetic markers.
What is genetic variation found in individuals who are of different racial or ethnic backgrounds? The definition of “racial” differs between scientific disciplines and in different societies and cultures. Generally, cultural and societal differences have been regarded as determining factors for differences in physical characteristics and traits among members of different racial or ethnic groups. For example, Europeans are typically thought to have a greater variation than Asian individuals in height, hair color, or skin pigmentation. Similarly, within African-American and Hispanic populations, individuals with similar phenotypic (racial) characteristics may also have substantial differences in physical characteristics, even if they live within the same racial or ethnic group.
Scientists examine variations in individuals using several methods. One method is by testing a collection of variants on a single locus, or set of loci. This collection must be done with an overall focus on a single population of interest to ensure a significant number of variants are present in that population, otherwise the test would be worthless. Testing for multiple minor loci is more commonly used in research settings.
The method of testing for genetic variability is known as coalescent analysis. It is the use of highly sensitive sequencing and PCR technologies to look for variation within a sample over a very long run. This type of analysis can reveal subtle differences over vast stretches of the genome-analogous to sexual reproduction. For example, sequences within the coding region can show variation related to the function of the genes involved in coding. However, it may be possible to distinguish between amino acid residues that affect the transcriptional process. It may even be possible to differentiate among differentially expressed proteins, or alternatively expressed proteins from a single gene.
Within non-homosexuals, genetic variations can be due to horizontal and vertical transmission through various forms of asexual reproduction. Horizontal transmission occurs when an individual’s genetic makeup is highly conserved across many copies of a gene, whereas vertical transmission only occurs when traits are highly monogenic or identical between organisms. Monogenic mutations are believed to have arisen due to gene flow between closely related species. There is some evidence that this type of variation is common in humans, but its origin is not well understood. Evidence of horizontal and vertical transmission can also be found in bacteria, where horizontal and vertical transmission has been observed in some cases. Again, understanding these patterns can provide important clues about their relationship to sexual reproduction.
Gene-based variations that result in variations in an individual’s DNA sequence are called genetic mutations. The term mutation can also be used to refer to differences caused by alterations in the DNA sequence. These modifications, called variants, can occur without any changes in the DNA sequence itself. They may be caused by insertions, deletions, and rearrangements in the DNA sequence.