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A heterozygote advantage describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. Loci exhibiting heterozygote advantage are a small minority of loci. [1] The specific case of heterozygote advantage due to a single locus is known as overdominance.
An obligate carrier is an individual who may be clinically unaffected but who must carry a gene mutation based on analysis of the family history; usually applies to disorders inherited in an autosomal recessive and X-linked recessive manner.
Most balanced translocation carriers are healthy and do not have any symptoms. It is important to distinguish between chromosomal translocations that occur in germ cells, due to errors in meiosis (i.e. during gametogenesis), and those that occur in somatic cells, due to errors in mitosis. The former results in a chromosomal abnormality featured ...
Overdominance is a phenomenon in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage regulated by a single genomic locus, wherein heterozygous individuals have a higher fitness than homozygous individuals.
One of the first genetic testing programs to identify heterozygote carriers of a genetic disorder was a program aimed at eliminating Tay–Sachs disease. This program began in 1970, and over one million people have now been screened for the mutation. [51]
Genetic counseling and genetic testing is offered to families that may be carriers of chromosomal translocations. [12] Rarely, the same translocation may be present homozygously if heterozygous parents with the same Robertsonian translocation have children. The result may be viable offspring with 44 chromosomes. [13]
In medical genetics, compound heterozygosity is the condition of having two or more heterogeneous recessive alleles at a particular locus that can cause genetic disease in a heterozygous state; that is, an organism is a compound heterozygote when it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be ...
The loss of heterozygosity is a common occurrence in cancer development. Originally, a heterozygous state is required and indicates the absence of a functional tumor suppressor gene copy in the region of interest.