One nucleotide is deleted near the start of a coding region in gene X. In gene Y, three consecutive nucleotides are deleted at a similar position. Which prediction is most likely?
Answer and explanation
Correct answer: B. Gene X is likely to be non-functional
- Step 1: A deletion of one nucleotide shifts the reading frame, so every later codon changes and a premature stop codon is likely.
- Step 2: A deletion of three nucleotides removes a whole codon (or merges two), keeping the frame, so only one amino acid is lost or changed.
Answer
gene X is likely non-functional; gene Y loses about one amino acid.
Why not the others: The option 'Gene Y is likely to give a non-functional protein' is reversed; the option 'Both proteins are likely to be non-functional' assumes all deletions are equally damaging; tRNA has no proofreading role for missing bases.
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