Classify point mutations and frameshift mutations by their effect on the resulting protein.
A mutation is any change in a DNA sequence, arising either from a replication error that slips past proofreading (Unit 7) or from exposure to a mutagen, such as ultraviolet light, certain chemicals, or radiation. A point mutation substitutes just one base, and falls into one of three categories depending on its effect: a silent mutation still codes for the same amino acid, thanks to redundancy in the genetic code (several different codons can specify the same amino acid); a missense mutation codes for a different amino acid, which may or may not change the protein's function depending on where and how it occurs; and a nonsense mutation creates a premature stop codon, usually severely truncating and breaking the resulting protein.
A frameshift mutation -- the insertion or deletion of a base -- is typically far more disruptive than a substitution, because it shifts the entire downstream reading frame, scrambling every codon that follows it, directly recalling last week's codon-by-codon reading. The effects of mutations overall range from neutral (no effect at all, especially for silent mutations or mutations in non-coding regions) to harmful (disrupted protein function, a genetic disorder, or, if a cell-cycle control gene is hit, cancer, as covered in Unit 5) to, rarely, beneficial in a particular environment. Mutation is described as the raw material of evolution for exactly this reason: it is the ultimate original source of all new genetic variation, and without new variation, natural selection would have nothing new to act on.
Mastery looks like: They can classify a point mutation as silent, missense, or nonsense from its effect on the resulting codon, and explain why frameshift mutations are typically more disruptive.
Common stumbles: Assuming any mutation must be harmful or dramatic; confusing a frameshift (insertion or deletion) with a simple substitution.