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Unformatted text preview: gene.
affect one gene Three major types of
• Which type of mutations
usually change the
protein sequence most?
one base changed • Why?
• When will an insertion
or deletion not cause a
frameshift? multiples of 3 wont do much damage alter many codons • When will a substitution
most severely affect the
protein? when it’s changed to a stop codon/early termination codon Transitions vs. transversions: • A transition is a substitution of a purine for a purine or a
pyrimidine for a pyrimidine. • A transversion is a substitution of a purine for a pyrimidine or
vice-versa Phenotypic effects of mutations:
Base substitutions • Three types of base substitutions:
• missense (changes amino acid sequence)
• nonsense (changes amino acid to a “stop”)
• silent (no change in amino acid sequence) change one base, results in new codon stop codon, nothing after stop codon (no other AA)
terminate proteins, protein is nonfunctional if it
happens too early does not change AA sequence Phenotypic effects of mutations:
Base substitutions does not matter as long as there isnt a huge space between two codons • A neutral mutation is a missense mutation that alters the amino
acid sequence of the protein, but does not change its function. • The amino acid may be replaced by another that is similar
• The affected amino acid may have little inﬂuence on protein
function. For Tomorrow: Finish Chapter 18: Mutation and DNA Repair...
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