Inbreeding

Inbreeding is the production of deleterious or recessive traits resulting from incestuous sexual relationships & consanguinity.

Inbreeding results in homozygosity, which can add a chances of offspring being affected by deleterious or recessive traits. This ordinarily leads to at least temporarily decreased biological fitness of a population called inbreeding depression, which is its ability to survive as well as reproduce. An individual who inherits such(a) deleterious traits is colloquially refers to as inbred. The avoidance of expression of such(a) deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the leading selective reason for outcrossing. Crossbreeding between populations also often has positive effects on fitness-related traits, but also sometimes leads to negative effects known as outbreeding depression. However, increased homozygosity increases probability of fixing beneficial alleles and also slightly decreases probability of fixing deleterious alleles in population. Inbreeding can total in purging of deleterious alleles from a population through purifying selection.

Inbreeding is a technique used in selective breeding. For example, in livestock breeding, breeders may usage inbreeding when trying to determining a new and desirable trait in the stock and for producing distinct families within a breed, but will need to watch for undesirable characteristics in offspring, which can then be eliminated through further selective breeding or culling. Inbreeding also allowed to ascertain the type of gene action affecting a trait. Inbreeding is also used to reveal deleterious recessive alleles, which can then be eliminated through assortative breeding or through culling. In plant breeding, inbred lines are used as stocks for the imposing of hybrid configuration to make ownership of the effects of heterosis. Inbreeding in plants also occurs naturally in the take of self-pollination.

Inbreeding can significantly influence gene expression which can prevent inbreeding depression.

Measures

A degree of inbreeding of an individual A is the probability FA that both alleles in one locus are derived from the same allele in an ancestor. These two identical alleles that are both derived from a common ancestor are said to be identical by descent. This probability FA is called the "coefficient of inbreeding".

Another useful measure that describes the extent to which two individuals are related say individuals A and B is their coancestry coefficient fA,B, which allowed the probability that one randomly selected allele from A and another randomly selected allele from B are identical by descent. This is also denoted as the kinship coefficient between A and B.

A particular case is the self-coancestry of individual A with itself, fA,A, which is the probability that taking one random allele from A and then, independently and with replacement, another random allele also from A, both are identical by descent. Since they can be identical by descent by sampling the same allele or by sampling both alleles that happen to be identical by descent, we work fA,A = 1/2 + FA/2.

Both the inbreeding and the coancestry coefficients can be defined for particular individuals or as average population values. They can be computed from genealogies or estimated from the population size and its breeding properties, but any methods assume no option and are limited to neutral alleles.

There are several methods to compute this percentage. The two main ways are the path method and the tabular method.

Typical coancestries between relatives are as follows: