Pros and Cons of Inbreeding

Inbreeding is the mating of closely related organisms or individuals. Generally, mating falls into inbreeding or outbreeding. While inbreeding involves closely related individuals, outbreeding involves individuals that are not related at all. For instance, inbreeding involves the mating of parent animals with their offspring, or the mating of the offspring of the same parents. Inbreeding has certain disadvantages and advantages.

Emphasizing Desirable Traits

• An advantage of inbreeding is to emphasize a desirable trait. Farmers often use inbreeding to "fix," or increase desirable traits through successive generational lines. For example, if the desired trait is a certain coat color or animal characteristic, limiting the diversity of gene pool will ensure that that trait does not get watered down in the following generation. Instead, the desired trait will be maintained in successive generations.

Undesirable Traits

• Unfortunately, the same process by which the desirable trait is fixed or increased with successive generations also leads to the emphasis of any undesirable traits further down the generational line. For example, a natural propensity to low milk production may be strengthened and manifest itself with each successive generation, leading to abnormally low production of milk in later generations. Farmers usually control such birth defects through the process of culling, where they destroy the animals with the undesirable characteristics.

Autosomal Recessive Genes

• One of the negative consequences of inbreeding is the development of autosomal recessive disorders by the inbred organisms. In genetics, an allele is a recessive gene that causes detectible characteristics, also known as a phenotype. Offspring that are the product of inbreeding may carry two copies of the same allele from their closely related parents. This cause a recessive genetic trait to become manifest in the offspring. Examples of recessive traits that may become apparent include anemia, sickle-cell, cystic fibrosis and glycogen storage diseases.

Identifying Recessive Genes

• According to information from the University of Missouri Agricultural Extension, breeders also use inbreeding to identify which animals are carriers of unwanted recessive genes. This is especially important for commercial breeders. According to the University of Missouri, the males are usually used to test for recessive traits. For instance, if the undesirable recessive trait is dwarfism in their cattle, they can use inbreeding to "out" the male carriers. This can be achieved by mating a male carrier to more than 35 of his daughters. If the male is responsible for the dwarfism, some of the female cattle will give birth to calves with the dwarfism trait. On the other hand, a male that is free of the recessive gene will produce offspring that do not have any such birth defect.

Reduction in Fitness of the Population

• Inbreeding limits the gene pool available to a population, leading to the recycling of the same genes in each generation an effect known as homozyngosity. This reduces the diversity of the population and leads to a general decrease in the general fitness of the population. Inbreeding leads to lower fertility and higher mortality rates among the members of the population.