Interpret mutation effects carefully

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or a browser document for a labeled drawing, table or explanation.
• Worked problem inputs: A supplied code table maps two different codons to the same amino acid. A substitution changes one into the other. Infer the coding effect.
• Assessment case 1: A supplied code table maps AAA and AAG to the same amino acid; AAA changes to AAG. What follows? Which inference or prediction is best supported?
• Assessment case 2: Which scientific label fits the specifically described step or feature? Supplied case: Supplied codon changes amino acid.
• Assessment case 3: Which scientific label fits the specifically described step or feature? Supplied case: Supplied codon becomes STOP.
• Assessment case 4: Which scientific label fits the specifically described step or feature? Supplied case: Single-base insertion shifts later codons.
• Assessment case 5: Which scientific label fits the specifically described step or feature? Supplied case: Different codons share same listed amino acid.
• Assessment case 6: Deleting the first A from AAAGCU changes groups from AAA GCU to AAG CU in the same frame. What follows? Which inference or prediction is best supported?

Learn the idea

A DNA change can be neutral, harmful or beneficial depending on context. Some coding changes preserve amino-acid sequence; others alter it. Do not use classroom examples to diagnose a real person.

Synonymous means changed codon encodes same amino acid in supplied table. Missense means changed codon encodes different amino acid. Nonsense means changed codon becomes a stop signal. Frameshift means base addition or loss alters downstream grouping.

For the supplied mechanism problem, A supplied code table maps two different codons to the same amino acid. A substitution changes one into the other. Infer the coding effect. The change is synonymous under that table because the encoded amino acid is unchanged. It is still a sequence mutation; lack of amino-acid change does not mean no possible biological effect elsewhere.

1. Read the supplied problem and mark the structures, processes or quantities named: A supplied code table maps two different codons to the same amino acid. A substitution changes one into the other. Infer the coding effect.
2. Draw the relevant boundary, pathway or comparison and label it using the scientific ideas above.
3. Write a causal explanation or calculation, showing how each observation supports the result.
4. Compare your reasoning with the worked solution; name a condition that would change or limit the inference.

Check your reasoning

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Take it further

New supplied code table maps UUU and UUC to the same amino acid, while UUA maps differently. Expected: UUU→UUC is synonymous under this table; UUU→UUA is missense under it.

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