BIOL 221 Chapter Notes - Chapter 6: Phenylalanine Hydroxylase, Osteogenesis Imperfecta, Null Allele
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Allelic series/ multiple alleles = known mutant alleles of a gene and its wild type allele. Dominance is a manifestation of how alleles of a single gene interact in a heterozygote. Interacting alleles may be +/m (wild type and mutant), or m1/m2 (2 different mutant allels) Allele expressed in phenotype when only 1 copy is present in a heterozygote. Cannot be distinguished from heterozygote phenotypically, a/a phenotype = a/a phenotype. Eg. pku = good model for recessive mutations (pah) > caused by defective allele of gene encoding enzyme, phenylalanine hydroxylase. > absence of normal pah -> phenylalanine enters body in food/ not broken down -> accumulates. > phenylalanine -> phenylpyruvic acid, which is transported to brain via blood -> mental retardation/ normal development impeded. > one dose of wt allele p produces enough pah to break down phenylalanine entering body. Haplosufficient = ability of single dose of allele to produce wild type phenotype.
