HMB265H1 Lecture Notes - Lecture 4: Null Allele, Phenylalanine Hydroxylase, Wild Type
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HMB265H1 Full Course Notes
Verified Note
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Document Summary
There are two broad categories to classify gene interactions: Interactions between alleles of one locus-variations on dominance. Interactions between two or more loci-reveal the number and types of genes: interactions between alleles of a single locus: variations on dominance. The known mutant alleles of a gene and its wild-type allele are referred to as multiple alleles or an allelic series. The simplest type of dominance is full or complete dominance. A fully dominant allele will be expressed when only one copy is present (dd or. Phenylketonuria (recessive disease) is caused by a defective allele of the gene encoding for the enzyme phenylalanine hydroxylase. In the absence of pah, the eaten phenylalanine is not broken down, accumulates, turns into phenylpyruvic acid, which is then transferred to the brain via bloodstream and impedes normal development and results in mental retardation. Fully dominant mutations can be said to be haploinsufficient; one dose is not enough to achieve normal levels of function.
