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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 ...
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 ...
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]
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 ...
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 ...
An amorphic allele elicits the same phenotype when homozygous and when heterozygous to a chromosomal deletion or deficiency that disrupts the same gene. [2] This relationship can be represented as follows: m/m = m/Df An amorphic allele is commonly recessive to its wildtype counterpart.
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.
Most often, this disease affects males whose mother is a carrier (heterozygous) for the disorder. Because females have two X-chromosomes, the mother will not be affected by carrying only one abnormal X-chromosome, but any male children will have a 50% chance of being affected with the disorder by inheriting the faulty gene.