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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 ...
A review of the genetics of inbreeding depression in wild animal and plant populations, as well as in humans, led to the conclusion that inbreeding depression and its opposite, heterosis (hybrid vigor), are predominantly caused by the presence of recessive deleterious alleles in populations. [7]
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]
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.
Very few phenotypes are purely Mendelian traits. Common violations of the Mendelian model include incomplete dominance, codominance, genetic linkage, environmental effects, and quantitative contributions from a number of genes (see: gene interactions, polygenic inheritance, oligogenic inheritance). [1] [2]
The most common X-linked recessive disorders are: [7] Red–green color blindness, also known as daltonism, [8] which affects roughly 7% to 10% of men and 0.49% to 1% of women. Its relative benignity may explain its commonness. Hemophilia A, a blood clotting disorder caused by a mutation of the Factor VIII gene and leading to a deficiency of ...