random changes in the frequency of alleles in a population. In small populations, it can lead to the elimination of a particular allele by chance alone. It is thought to be one cause of speciation when a group of organisms is separated from its parent population
Changes in gene/allele frequencies in a POPULATION over many GENERATION resulting from chance rather than SELECTION. Occurs most rapidly in small populations. Can lead to some ALLELE becoming `extinct', thus reducing the genetic variability in the population.
A gradual (or sometimes abrupt) change in the germplasm balance of a cross-pollinated cultivar causing a change in its characteristics. Usually applies to grasses or legume cultivars when seed is produced outside their area of adaption. The shift may be caused by selective differences in plant mortality or flowering habit under the different environment.
the cumulative effect of the chance loss of some genes and the disproportionate replication of others over successive generations resulting in the frequency of the alleles altering from one generation to the next in small populations.
Refers to the constant tendency of genes to evolve even in the absence of selective forces. Genetic drift is fuelled by spontaneous neutral mutations that disappear or become fixed in a population at random. Inbred lines separated from a common ancestral pair can drift rapidly apart from each other.
The fact that chance, rather than selection, may affect gene frequencies when a population is very small (usually fewer than fifty individuals). This phenomenon, like that of the founder principle, is due to "sampling error". genotype The genetic constitution of an individual organism.
In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). The effect may cause an allele and the biological trait that it confers to become more common or more rare over successive generations. Ultimately, the drift may either remove the allele from the gene pool or remove all other alleles.