BIOL 2299 Lecture Notes - Lecture 4: Transferase, Melanin, Penetrance
15 Sep 2016
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Document Summary
Results in severe physical and mental disability and ultimately in deat. Individuals often have children before they even realize they have disease, therefore trait commonly gets passed from one generation to next. Caused by trinucleotide repeat expansion in gene coding for huntingtin(htt)-one of several polyglutamine disease. ~ offspring of affected individual are affected. Example: albinism=absence of pigment in skin, hair, and iris of the eyes. Many related to defects in tyrosinase enzyme. Most affected persons have parents who are not affected. Parents are heterozygous for recessive allele(called carriers) Approximate children of two carriers are affected. The parents of affected individuals are often relatives. Was thought to be an autosomal recessive. Phenotype of heterozygous genotype is intermediate between the phenotypes of the homozygous genotyes. Incomplete dominance is often observed when the phenotype is quantitative rather than discrete. Codominance means that the heterozygous genotype exhibits the traits associated with both homozygous genotypes.
