BIO 325 Study Guide - Midterm Guide: Reproductive Isolation, Nonsense Mutation, Purine
• Substitution
o Transitions – replaces the base with one from a similar category (purine to
purine A to G) transitions replace A with G
o Transversions – replaces the base from a different category (purine to
pyrimidine A to C or G to T) transversions replace A with C or G with T
o Purines (A+G, 2 rings) for purines; pyrimidine (T+C, one ring) for pyrimidine
o Effects of Substitutions
▪ Exons
▪ “yoyous silet Mutations (A to G)
• No effect
• Silent mutation cause change in base, but amino acid remains the
same
• Genetic code is redundant
• ATG CGA GTG change to ATG CGG GTG
▪ Missense Mutations (C to G)
• Maybe effect
• Missense mutations cause base change, resulting an amino acid
to change
• ATG CGA GTG change to ATG GGA GTG
▪ Nonsense Mutations (C to T)
• Usually an effect
• Nonsense mutation cause base to change, resulting a stop codon
• ATG CGA GTG change to ATG TGA (STOP) GTG
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