Inbreeding facts for kids
Inbreeding is a term in genetics, meaning the crossing (mating) of closely related animals or plants. Self-fertilisation in plants is the most extreme kind of inbreeding. It is quite widespread in plants which carry both male and female flowers on the same plant. Inbreeding is the opposite of outcrossing, which is the mating of unrelated members of the same species.
For human beings, inbreeding is a very destructive trait, and almost all cultures in the world have attempted to restrict inbreeding e.g. by prohibiting marriages between first cousins.
Contents
Effects
When inbreeding happens over several generations in a group, it reduces genetic diversity. This can lead to:
- Increased chance of inheriting certain traits: This can be good or bad. If the related parents both have genes for a desirable trait (like a specific color in a flower or speed in a racehorse), their offspring are more likely to get two copies and show that trait strongly. This is sometimes used by people in selective breeding.
- Increased chance of inheriting less helpful traits: This is the main concern with inbreeding. Many genes have versions that don't cause problems unless you get two copies of them (one from each parent). Closely related parents are more likely to both carry the same version of these genes. When their offspring get two copies, it can lead to health problems or make them less able to survive. This is sometimes called "inbreeding depression."
- Reduced ability to adapt: With less genetic diversity, the group has fewer different "tools" (gene versions) to deal with changes in their environment, like new diseases or climate change.
In nature
Cheetahs are an example of inbreeding. Thousands of years ago, the cheetah went through a population bottleneck that reduced its population dramatically so the animals that are alive today are all related to one another. A consequence from inbreeding for this species has been high juvenile mortality, low fecundity, and poor breeding success.
In a study on an island population of song sparrows, individuals that were inbred showed significantly lower survival rates than outbred individuals during a severe winter weather related population crash. These studies show that inbreeding depression and ecological factors have an influence on survival.
Royalty and nobility
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Inter-nobility marriage was used as a method of forming political alliances among elites. These ties were often sealed only upon the birth of progeny within the arranged marriage. Thus marriage was seen as a union of lines of nobility and not as a contract between individuals.
Royal intermarriage was often practiced among European royal families, usually for interests of state. Over time, due to the relatively limited number of potential consorts, the gene pool of many ruling families grew progressively smaller, until all European royalty was related. This also resulted in many being descended from a certain person through many lines of descent, such as the numerous European royalty and nobility descended from the British Queen Victoria or King Christian IX of Denmark.
Interesting facts about inbreeding
- Island species are often very inbred, as their isolation from the larger group on a mainland allows natural selection to work on their population.
- Linebreeding is a form of inbreeding. There is no clear distinction between the two terms, but linebreeding may encompass crosses between individuals and their descendants or two cousins. This method can be used to increase a particular animal's contribution to the population.
- The House of Habsburg was known for its intermarriages; the Habsburg lip often cited as an ill-effect.
Related pages
Images for kids
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Common fruit fly females prefer to mate with their own brothers over unrelated males.
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Heterozygous
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White tiger in Gunma Safari Park
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Hereditary polycystic kidney disease is prevalent in the Persian cat breed, affecting almost half the population in some countries.
See also
In Spanish: Endogamia (biología) para niños
