User:Piper5625/Genetic variability

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Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype, or the presence of genotypically different individuals, in contrast to environmentally induced differences which, as a rule, cause only temporary, nonheritable changes of the phenotype". Genetic variability in a population is important for biodiversity, as it ensures that no two living things are exactly alike. While there are many sources that can cause genetic variability, there are also factors that can decrease genetic variability.

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Causes
 * Homologous recombination is a significant source of variability. During meiosis in sexual organisms (sexual reproduction), two homologous chromosomes cross over one another and exchange genetic material. The chromosomes then split apart and are ready to contribute to forming an offspring. This random process of exchanging genetic material is known as recombination, and it is governed by its own set of genes.  Being controlled by genes means that recombination is variable in frequency. Generally, it is more common in areas on the chromosome where there are a higher number of genes. It creates more combinations of genes. 
 * Polyploidy – having more than two homologous chromosomes allows for even more recombination during meiosis allowing for even more genetic variability in one's offspring. However, this phenomenon can also prove difficult for cell division. 


 * Genetic mutations – contribute to the genetic variability within a population and can have positive, negative, or neutral effects on a fitness. This variability can be easily propagated throughout a population by natural selection if the mutation increases the affected individual's fitness and its effects will be minimized/hidden if the mutation is deleterious. If the individual can survive with the mutations they have, those mutations will likely be passed down to offspring. However, the smaller a population and its genetic variability are, the more likely the recessive/hidden deleterious mutations will show up causing genetic drift.
 * DNA damages are very frequent, occurring on average more than 60,000 times a day per cell in humans due to metabolic or hydrolytic processes as summarized in DNA damage (naturally occurring). Most DNA damages are accurately repaired by various natural DNA repair mechanisms. However, some DNA damages remain and give rise to mutations.
 * Additionally, not all types of mutations occur as much as others do. Some mutations might have a huge impact on the human body, and some might not. It depends on what combination of base pairs is changed. 

See also[edit]

 * Evolvability
 * Human genetic variation
 * Personalized medicine
 * Microevolution
 * Mutation
 * Genetic drift
 * Gene flow
 * Glossary of genetics and evolutionary biology