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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 ...
Because the genetic disorder is incompletely recessive, a person with only one SCA allele and one unaffected allele will have a "mixed" phenotype: The sufferer will not experience the ill effects of the disease, yet will still possess a sickle cell trait, whereby some of the red blood cells undergo benign effects of SCA, but nothing severe ...
In X-linked recessive disorders, only females can be the carriers of the recessive mutation, making them obligate carriers of this type of disease. Females acquire one X-chromosome from their father and one from their mother, and this means they can either be heterozygous for the mutated allele or homozygous. If heterozygous, she is a carrier ...
Sickle-cell disease and the associated trait are most prevalent in Africa and Central America, which is attributed to natural selection: the sickle-cell trait confers a survival advantage in areas with a high occurrence of malaria, which has a high death rate among individuals without the trait. [citation needed]
The heterozygous and homozygous phenotype is still expressed in most cases if two different disease-causing alleles are present. Achondroplasia is a skeletal system disorder caused by a recessive allele that can still result in a live birth in the homozygous state.
It is an autosomal recessive disorder, requiring either homozygosity or double heterozygosity for disease manifestation. Diagnostic tools include assessing the ratio of VWF binding to VWF antigen levels. [25] A ratio <0.3 indicates homozygous or double heterozygous VWD Type 2N, while a ratio <0.5 suggests heterozygous VWD Type 2N. Conversely, a ...
In an individual which is heterozygous regarding a certain allele, it is not externally recognisable that it also has the recessive allele. But if the carrier has a child, the recessive trait appears in the phenotype, in case the descendant receives the recessive allele from both parents and therefore does not possess the dominant allele that ...
Raine syndrome appears to be an autosomal recessive disease. There are reports of recurrence in children born of the same parents, and an increased occurrence in children of closely related, genetically similar parents. Individuals with Raine syndrome were either homozygous or compound heterozygous for the mutation of FAM20C.