BIO 111 Lecture Notes - Lecture 19: Dna Replication, Hypoxanthine, Complementary Dna
Document Summary
Gene mutation: a small change in the structure of a single gene. One way new genes (traits) can be created! Based on how the mutation affects gene expression: silent mutations, missense mutations, nonsense mutations, frameshift mutations, silent mutations: do not alter aa sequence! Codon happens to code for the same amino acid! Mutant gene functions exactly the same as normal gene: missense mutation: changes a single amino acid in a polypeptide chain. May or may not alter protein function. Sickle cell anemia is caused by a missense mutation. Generally harmful, except in tropical regions with malaria: nonsense mutation. Change from a normal codon to a stop codon. Hurler syndrome due to enzyme deficiency, causes progressive organ damage & eventually death: frameshift mutation: addition or deletion of nucleotides that are not multiples of 3. Tay-sachs enzyme to break down gangliosides defective; neuron cells in brain & body deteriorate. Mutations in promoter & regulatory regions can alter gene expression.