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Introduction to Genetic Analysis (Introduction to Genetic Analysis (Griffiths))

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Chapter 15: Mutation, Repair, and Recombination (15.1-15.3) I) Genetic variation arises from mutation and recombination A) Mutation is the ultimate source of evolutionary change B) Recombination causes alleles of different genes to become grouped into new combinations II) Types of DNA mutations A) Point mutations—alteration of a single base pair of DNA or of a small number of adjacent base pairs 1) Types of point mutations a) Base substitutions i) Transition—replacement of a base by the other base in the same chemical category (i.e. a purine for a purine, A↔G or a pyrimidine for a pyrimidine, C↔T), more common ii) Transversion—replacement of a base of one chemical category with a base of the other (pyrimidine is replaced by purine and vice versa, A↔C, A↔T, G↔T, G↔C) b) Indel mutations—insertions or deletions of nucleotide pairs 2) Consequences of point mutations in coding regions a) Synonymous (silent) mutations—one codon for an amino acid is changed into another codon for the same amino acid b) Missense mutations (nonsynonymous)—one amino acid is changed into a codon for another amino acid i) Conservative substitution—amino acid is replaced with one that is chemically similar, less likely to affect protein structure/function ii) Nonconservative substitution—amino acid replaced with a chemically different one c) Nonsense mutations—codon for one amino acid is changed into a stop codon d) Single base pair changes that inactivate proteins are often due to splice site mutations e) Frameshift mutations—addition or deletion of a single base pair that
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