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Autosomal dominant A 50/50 chance of inheritance. Sickle-cell disease is inherited in the autosomal recessive pattern. When both parents have sickle-cell trait (carrier), a child has a 25% chance of sickle-cell disease (red icon), 25% do not carry any sickle-cell alleles (blue icon), and 50% have the heterozygous (carrier) condition. [1]
The avoidance of expression of such deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the main selective reason for outcrossing. [6] [7] Crossbreeding between populations sometimes has positive effects on fitness-related traits, [8] but also sometimes leads to negative effects known as outbreeding ...
The major histocompatibility complex genes, or MHC genes, have been implicated in kin recognition. [21] One idea is that the MHC genes code for a specific pheromone profile for each individual, which are used to discriminate between kin and non-kin conspecifics. Several studies have demonstrated the involvement of the MHC genes in kin recognition.
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).
[1] Inbreeding depression is the reduced biological fitness that has the potential to result from inbreeding (the breeding of related individuals). The loss of genetic diversity that is seen due to inbreeding, results from small population size. [2] Biological fitness refers to an organism's ability to survive and perpetuate its genetic material.
Mendelian traits behave according to the model of monogenic or simple gene inheritance in which one gene corresponds to one trait. Discrete traits (as opposed to continuously varying traits such as height) with simple Mendelian inheritance patterns are relatively rare in nature, and many of the clearest examples in humans cause disorders.
Carrier testing is a type of genetic testing that is used to determine if a person is a carrier for specific autosomal recessive diseases. [1] This kind of testing is used most often by couples who are considering becoming pregnant to determine the risks of their child inheriting one of these genetic disorders. [2]
Illustration of chromosome crossover during genetic recombination. In evolutionary genetics, Muller's ratchet (named after Hermann Joseph Muller, by analogy with a ratchet effect) is a process which, in the absence of recombination (especially in an asexual population), results in an accumulation of irreversible deleterious mutations.