Question

mutation
learning objective 23.3: given a specific change in a dna coding strand, predict the consequences for the gene product.
which of these mutations in a gene would likely result in no protein product being made at all? select all that apply.
□ a single-base mutation in the gene’s promoter that prevents rna polymerase from binding to the promoter
□ a single-base mutation in the stop codon
□ a single-base mutation in the transcription termination site
□ a single-base mutation in the start codon
incorrect.

• a mutation in the transcription termination site may result in a longer mrna than usual, but does not affect the protein-coding region made the mrna and would not completely prevent the protein from being translated.

Explanation:

1. Promoter Mutation: The promoter is where RNA polymerase binds to start transcription. If a mutation in the promoter prevents RNA polymerase from binding, transcription (the first step to make mRNA, which is then translated to protein) won't occur. So no mRNA is made, hence no protein.
2. Start Codon Mutation: The start codon (e.g., AUG) is the signal for the ribosome to start translating mRNA into a protein. A mutation here can prevent the ribosome from initiating translation. If translation doesn't start, no protein is synthesized.
3. Stop Codon Mutation: A mutation in the stop codon typically causes the ribosome to keep translating (a frameshift or extended protein), but it doesn't prevent protein production entirely—just changes the protein. So this is incorrect.
4. Transcription Termination Site Mutation: As explained, this leads to a longer mRNA but doesn't stop translation of the protein - coding region. So protein is still made (maybe longer), so this is incorrect.

Answer:

• a single - base mutation in the gene’s promoter that prevents RNA polymerase from binding to the promoter
• a single - base mutation in the start codon