Skin grafting and other methods indicated inbreeding within the demes, but sharing of certain alleles between the demes suggested a continuous gene flow between demes.

Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase of its frequency.

Directional or positive selection refers to a situation where a certain allele has a greater fitness than other alleles, consequently increasing its population frequency (e.g. antibiotic resistance of bacteria).

A second effect is "G x E correlation", in which certain alleles tend to accompany certain environments.

The clines of hybrid zones can be observed by recording the frequency of certain diagnostic alleles or phenotypic characteristics for either population along a transect between the two populations.

This new population's allelic frequency is probably different from the original population's, and will change how common certain alleles are in the populations.

Genetic Linkage studies attempt to find a correlation between the diagnosis and inheritance of certain alleles within families who have two or more ill relatives.

In humans, certain alleles of this gene have been statistically associated with an increased risk of developing late-onset Alzheimer's disease.

In addition, the color white in horses, when created by certain alleles of "dominant white" (W) gene, may possibly be fatal if homozygous.

What may make the bottleneck effect a sampling error is that certain alleles, due to natural disaster, are more common while others may disappear completely, making it a potential sampling error.