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Factor V Leiden is an autosomal dominant genetic condition that exhibits incomplete penetrance, i.e. not every person who has the mutation develops the disease. The condition results in a factor V variant that cannot be as easily degraded by activated protein C. The gene that codes the protein is referred to as F5.
In the more significant of the two, the individual is homozygous for the 677T polymorphism. This variant in particular is the most common genetic cause of hyperhomocysteinemia. [ 9 ] The resulting enzyme is thermolabile and in homozygotes, enzymatic activity is depressed to 35% of its usual level. [ 10 ]
The words homozygous, heterozygous, and hemizygous are used to describe the genotype of a diploid organism at a single locus on the DNA. Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus, hemizygous describes a genotype consisting of only a single copy of a particular gene in an ...
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 ...
Methylenetetrahydrofolate reductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the MTHFR gene. [5] Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. Natural variation in this ...
Heterozygous protein C deficiency occurs in 0.14–0.50% of the general population. [13] [14] Based on an estimated carrier rate of 0.2%, a homozygous or compound heterozygous protein C deficiency incidence of 1 per 4 million births could be predicted, although far fewer living patients have been identified. [6]
Haplosufficiency accounts for the typical dominance of the "standard" allele over variant alleles, where the phenotypic identity of genotypes heterozygous and homozygous for the allele defines it as dominant, versus a variant phenotype produced only by the genotype homozygous for the alternative allele, which defines it as recessive.
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.