Final answer:
The mutation that deletes a 'g' from a template strand could be suppressed by a second mutation that deletes exactly three base pairs downstream from the original mutation, potentially correcting the frameshift without altering the overall reading frame of the genetic code.
Step-by-step explanation:
The original nucleotide sequence of the template strand of a protein-encoding gene is 3' agccatac 5'. A mutation that deletes a single base pair, specifically the 'g' from this strand, would cause a frameshift mutation because the genetic code is read in groups of three nucleotides called codons. To suppress this mutation:
- Option A (a second base pair deletion close to but downstream from the original mutation within the same gene) would not correct the frameshift caused by the original mutation.
- Option B (a second mutation that adds a base pair close to but downstream) would not correct the original frameshift and might exacerbate it.
- Option C (a mutation creating a suppressor tRNA gene) might suppress the effects of the mutation but would not correct the frameshift in the original gene.
- Option D (a second mutation which deletes exactly three base pairs close to but downstream from the original mutation) could potentially correct the frameshift, as adding or removing nucleotides in multiples of three does not disrupt the overall reading frame.
Therefore, the mutation could be suppressed by a second mutation which deletes exactly three base pairs close to but downstream from the original mutation within the same gene. This is because restoring the reading frame would allow the genetic code to be read correctly downstream of the mutation, despite the insertion of an additional amino acid or the deletion of one to three amino acids. If not precisely managed, however, these alterations can still impact the protein structure and function.