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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 creation of hybrid lines to make use of the effects of heterosis. Inbreeding in plants also occurs naturally in the form of self-pollination.
However, inbreeding also gives opportunity for genetic purging of deleterious alleles that otherwise would continue to exist in population and could potentially increase in frequency over time. Another possible negative effect of inbreeding is weakened immune system due to less diverse immunity alleles as a result of outbreeding depression. [6]
Charles Darwin was one of the first scientists to demonstrate the effects of inbreeding depression, through numerous experiments on plants. Darwin's wife, Emma, was his first cousin, and he was concerned about the impact of inbreeding on his ten children, three of whom died at age ten or younger; three others had childless long-term marriages.
Genetic purging is the increased pressure of natural selection against deleterious alleles prompted by inbreeding. [1]Purging occurs because deleterious alleles tend to be recessive, which means that they only express all their harmful effects when they are present in the two copies of the individual (i.e., in homozygosis).
Inbreeding does not always result in negative fitness consequences, but when inbreeding is associated with fitness reduction it is called inbreeding depression. Inbreeding becomes of increasing concern as the level of homozygosity increases, facilitating the expression of deleterious alleles that reduce the fitness. Habitat fragmentation can ...
The child-rearing practices of the kibbutz system are sometimes cited as an example of the Westermarck effect. Seen here are a group of children in Kibbutz Gan Shmuel , circa 1935–40. The Westermarck effect , also known as reverse sexual imprinting , is a psychological hypothesis that states that people tend not to be attracted to peers with ...
Maybe she had children, and wanted to warn them about the wayward world beyond adolescence. Maybe her mother, or her mother's mother, told her the story, and as a child she delighted in its shocking twists and turns. Maybe it helped break up the mundanity of her domestic duties, or the telling of the story felt like a duty in itself.
Heterosis is often discussed as the opposite of inbreeding depression, although differences in these two concepts can be seen in evolutionary considerations such as the role of genetic variation or the effects of genetic drift in small populations on these concepts.