This is called the neutral hypothesis, or genetic drift.

Another likely explanation for the loss of its eyes is that of selective neutrality and genetic drift: in the dark environment of the cave, the eyes are neither advantageous nor disadvantageous and thus any genetic factors that might impair the eyes ( or their development ) can take hold with no consequence on the individual or species.

Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow.

** Microevolution: species — speciation — adaptation — selection — natural selection — directional selection — sexual selection — genetic drift — sexual reproduction — asexual reproduction — colony — allele frequency — neutral theory of molecular evolution — population genetics — Hardy-Weinberg principle

Using this method, scientists and farmers hope to keep the number of resistant genes very low, and use genetic drift to ensure any resistance that does emerge does not spread.

For example, Darwinism may be used to refer to Darwin's proposed mechanism of natural selection, in comparison to more recent mechanisms such as genetic drift and gene flow.

When populations within a species become isolated by geography, feeding strategy, mate selection, or other means, they may start to differ from other populations through genetic drift and natural selection, and over time may evolve into new species.

The study deduced from genetic drift in nuclear and mitochondrial DNA ( mtDNA ) that giraffes from these populations are reproductively isolated and rarely interbreed, even though no natural obstacles block their mutual access.

The role of genetic drift is equivocal ; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained.

This change is due to four different processes: mutation, selection ( natural and artificial ), gene flow, and genetic drift.

Ten simulations of random genetic drift of a single given allele with an initial frequency distribution 0. 5 measured over the course of 50 generations, repeated in three reproductively synchronous populations of different sizes.

In contrast to natural selection, which makes gene variants more common or less common depending on their reproductive success, the changes due to genetic drift are not driven by environmental or adaptive pressures, and may be beneficial, neutral, or detrimental to reproductive success.

The effect of genetic drift is larger in small populations, and smaller in large populations.

Vigorous debates wage among scientists over the relative importance of genetic drift compared with natural selection.

Ronald Fisher held the view that genetic drift plays at the most a minor role in evolution, and this remained the dominant view for several decades.

In 1968 Motoo Kimura rekindled the debate with his neutral theory of molecular evolution which claims that most of the changes in the genetic material are caused by genetic drift.

The predictions of neutral theory, based on genetic drift, do not fit recent data on whole genomes well: these data suggest that the frequencies of neutral alleles change primarily due to selection at linked sites, rather than due to genetic drift by means of sampling error.

These can accumulate over time due to genetic drift.

Although a complete theory of evolution also requires an account of how genetic variation arises in the first place ( such as by mutation and sexual reproduction ) and includes other evolutionary mechanisms ( such as genetic drift and gene flow ), natural selection appears to be the most important mechanism for creating complex adaptations in nature.

The spread of antibacterial resistance often occurs through vertical transmission of mutations during growth and by genetic recombination of DNA by horizontal genetic exchange.

This is the only form of sexual reproduction that occurs within the group, though it is really more genetic reorganization than reproduction.

The most significant and rapid genetic reorganization occurs in extremely small populations that have been isolated ( as on islands ).

* Recombination hotspot, a DNA position where genetic recombination occurs with above-average frequency

During this time disjunction occurs, which is one of the processes leading to genetic diversity as each chromosome can end up in either of the daughter cells.

Studies of retroviruses led to the first demonstrated synthesis of DNA from RNA templates, a fundamental mode for transferring genetic material that occurs in both eukaryotes and prokaryotes.

Insufficiency of the urea cycle occurs in some genetic disorders ( inborn errors of metabolism ), and in liver failure.

It remains controversial whether sufficient morphological and genetic divergence occurs within the genus as a result of geographical or ecological isolation to justify recognition of more than one species.

Most likely MS occurs as a result of some combination of genetic, environmental and infectious factors, and possibly other factors like vascular problems.

Huntington's disease is an incurable genetic disorder that occurs when neurons in the brain degenerate.

As such, the insensitivity to androgens is clinically significant only when it occurs in genetic males ( i. e. individuals with a Y-chromosome, or more specifically, an SRY gene ).

It is worthwhile to note that not every mutation of the AR gene results in androgen insensitivity ; one particular mutation occurs in 8 to 14 percent of genetic males, and is thought to adversely affect only a small number of individuals when other genetic factors are present.

Fragile X syndrome is a genetic disorder which occurs as a result of a mutation of the fragile X mental retardation 1 ( FMR1 ) gene on the X chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5 ' untranslated region of FMR1.

This so-called PWS / AS region may be lost by one of several genetic mechanisms which, in the majority of instances occurs through chance mutation.

It occurs as a sporadic mutation in approximately 75 % of cases ( associated with advanced paternal age ) or may be inherited as an autosomal dominant genetic disorder.

Currently, it is well understood how genetic mutation occurs.

Researchers have compared the prevalence of eczema in people who also suffer from celiac disease to eczema prevalence in control subjects, and have found that eczema occurs about three times more frequently in celiac disease patients and about two times more frequently in relatives of celiac patients, potentially indicating a genetic link between the two conditions.

An extremely large heart is a trait that occasionally occurs in Thoroughbreds, linked to a genetic condition passed down via the dam line, known as the " x-factor ".

It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis ( pachytene ) in a process called synapsis.

* Short legs in conjunction with eye abnormalities: Due to a genetic defect at the COL2A1 locus occurs on disproportionate dwarfism with short limbs in connection with cataracts, malformations of the retina and / or retinal detachment, liquefaction of the vitreous and a persistent hyaloid artery.

When a new phenotype with higher fitness occurs, its genotype sweeps through the population to fixation, and genetic diversity is reduced during a selectionist regime.

It is a genetic condition that occurs as a new mutation, and is rarely inherited.

Most colorectal cancer occurs due to lifestyle and increasing age with only a minority of cases associated with underlying genetic disorders.