Fixed allele

[2] Low genetic diversity is accompanied by allele fixation, which can potentially lead to lower adaptibility to changing environmental conditions for a population as a whole.

Hence, generally, populations exhibiting a significant range of fixed alleles are often at risk for extinction.

He credits the works of Haldane in 1927[6] and Fisher in 1922[7] as being important in providing foundational information that allowed him to come to his conclusion.

While there are many possibilities for how a fixed allele can develop, often multiple factors come into play simultaneously and guide the process, consequently determining the end result.

Natural selection was postulated by Charles Darwin and encompasses many processes that lead to the differential survival of organisms due to genetic or phenotypic differences.

One way some of these natural selection processes cause fixation is through one specific genotype or phenotype being favored, which leads to the convergence of the variability until one allele becomes fixed.

As antibiotics are used to kill bacteria, a small number of them with favorable mutations can survive and repopulate in an environment that is now free of competition.

A bottleneck occurs when a population is put under strong selective pressure, and only certain individuals survive.

To the right is an image that shows through successive generations; the allele frequencies fluctuate randomly within a population.

Investigation into three water buffalo populations revealed four different haplotypes each having a single nucleotide polymorphism (SNP), however, all of these SNPs were conservative mutations, causing no change in protein production.

[14] The Parnassius apollo butterfly is classified as a threatened species, having many disjointed populations in the Western Palaearctic region.

The population in the Mosel Valley of Germany has been genetically characterized and had been shown to have six long-term monomorphic microsatellites.

For example, the California Channel Island Fox (Urocyon littoralis) has the most monomorphic population ever reported for a sexually reproducing animal.

Image illustrating the concept of fixed alleles through comparing different populations of an imagined species.
For this hypothetical species, the population in the topmost frame exhibits no fixed allele for "color". In contrast, the populations depicted in the latter frames exhibit fixed alleles for "color" black, red and purple respectively.
This image shows how though successive generations random allele fluctuations, or genetic drift, can lead to the fixation or loss of certain alleles within a population.