BIO 190 Chapter Notes - Chapter 6: Osteogenesis Imperfecta, Phenylalanine Hydroxylase, Molar Concentration
16 Sep 2013
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Document Summary
In pku wt allele is dominant and the mutant is recessive that effects the gene encoding the enzyme pah that breaks down the phenylalanine entering the blood stream leading to accumulation of phe. However, the presence of heterozygote results in no pku because the pah gene is haplosufficient. Null mutation would lead to an inadequate amount concentration of an enzyme or protein in heterozygote form. This leads to conditions like defects in the development if pharyngeal arteries in mice with haploinsufficine ttbx1 gene. Polypeptides with this mutation act as spoilers and it binds to the wt polypeptide and distorts it or interferes with the function this occurs with homodimeric and heterodimeric proteins. When the gene product is a monomer the mutant binds to the substrate leaving very little to bind with the wildtype. The phenotype of the heterozygote is intermediate between those of the two homozygotes on some quantitative scale of measurement.
