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Autosomal dominant and autosomal recessive inheritance, the two most common Mendelian inheritance patterns. An autosome is any chromosome other than a sex chromosome.. In genetics, dominance is the phenomenon of one variant of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome.
Four different traits can be identified by pedigree chart analysis: autosomal dominant, autosomal recessive, x-linked, or y-linked. Partial penetrance can be shown and calculated from pedigrees. Penetrance is the percentage expressed frequency with which individuals of a given genotype manifest at least some degree of a specific mutant ...
Autosomal genetic disorders which exhibit Mendelian inheritance can be inherited either in an autosomal dominant or recessive fashion. [7] These disorders manifest in and are passed on by either sex with equal frequency. [7] [8] Autosomal dominant disorders are often present in both parent and child, as the child needs to inherit only one copy ...
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]
According to the model of Mendelian inheritance, alleles may be dominant or recessive, one allele is inherited from each parent, and only those who inherit a recessive allele from each parent exhibit the recessive phenotype. Offspring with either one or two copies of the dominant allele will display the dominant phenotype.
Certain other phenotypes, such as wet versus dry earwax, are also determined in an autosomal recessive fashion. [24] [25] Some autosomal recessive disorders are common because, in the past, carrying one of the faulty genes led to a slight protection against an infectious disease or toxin such as tuberculosis or malaria. [26]
Pseudodominance is the situation in which the inheritance of a recessive trait mimics a dominant pattern. [1]Normally, two recessive alleles need to be inherited (one from each parent) for the recessive trait to be expressed but recessive merely means that the trait is only expressed in the absence of the dominant alleles.
There are fewer X-linked dominant conditions than X-linked recessive, because dominance in X-linkage requires the condition to present in females with only a fraction of the reduction in gene expression of autosomal dominance, since roughly half (or as many as 90% in some cases) of a particular parent's X chromosomes are inactivated in females.