Chapter 15

Chapter 15 - Chapter 15 I. Phenotypic Consequences of DNA...

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Chapter 15 I. Phenotypic Consequences of DNA Mutations a. Point Mutations - alteration of a single base pair of DNA or of a small number of adjacent base pairs. i. Types of Point Mutations 1. Base Substitutions a. Transition- replacement of a base by the other base of the same chemical category (purine by a purine, pyrimidine by a pyrimidine) b. Transversion- replacement of a base of one chemical category by a base of the other (purine by a pyrimidine etc…) 2. Base insertions or deletions ( indel mutations ) a. Deletion or insertion of a single base pair ii. Molecular Consequences of point mutations in a coding region 1. Synonymous Mutations- mutation changes one codon for an amino acid into another codon for that same amino acid. Also called silent mutations… 2. Missense Mutations- codon for one amino acid is changed into a codon for another amino acid. Also called nonsynonymous mutations. 3. Nonsense Mutation- Codon for one amino acid is changed into a translation-termination (stop) codon. 4. Conservative Substitution- not very severe, replaces amino acid with a chemically similar amino acid. 5.
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Chapter 15 - Chapter 15 I. Phenotypic Consequences of DNA...

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