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changes in the gene
as part of 91157
| Term | Definition |
|---|---|
| Allele frequency | The proportion of an allele in the gene pool. Calculated as: number of that allele ÷ total number of all alleles for that gene in the gene pool. |
| population bottleneck | A population is suddenly reduced due to a catastrophic event to a few individuals and then recovers with low genetic diversity. |
| Founder effect | A new population is established by a small number of individuals from an existing (ancestral) population, with lower genetic diversity. |
| Genetic variation | The range of all the alleles in a population; the greater the number of different alleles present, the greater this is. |
| genetic drift | The change in allele frequencies in populations due to chance events (not selection). It may include the loss of alleles from a gene pool. The effects are greatest in small populations. |
| Natural selection | Phenotypes which are best suited to the environment have the greatest reproductive success. This changes the allele frequencies in the gene pool. |
| selection pressure | Anything that affects the survival and reproductive success of an individual |
| artificial selection | When humans select for alleles that are favourable to them and not necessarily the organism. This can artificially alter the alleles frequency in the gene pool and can reduce the ability of the organism to survive in nature. |
| Immigration | Individuals coming into the gene pool. Increases allele frequency and can introduce new alleles. |
| Emmigration | Individuals leaving the gene pool. decreases allele frequency and can reduce genetic diversity. |
| Migration | The movement of individuals and therefore alleles, into or out of a gene pool |
| Why genetic variation is important | Greater the diversity in alleles/ allele combinations, the greater the range of phenotypes, therefore when the environment chances there is increased chance some individuals will survive to continue the species. |