Question

If a single base-pair deletion occurred in the part of the gene that corresponds to the mRNA above and the resulting partial amino acid sequence was (N-term-...P-M-N...-C-term), which new partial mRNA sequence would be consistent with this change? Bases surrounding the deletion are underlined. Bases surrounding the deletion are underlined.

1) 5' - G | CCA | UCG | AAC | U - 3'

2) 5' - G | CCG | UCG | AAC | U - 3'

3) 5' - G | CCG | ACG | AAC | U - 3'

4) 5' - G | CCG | AUG | AAC | U - 3'

Answer 1

A single base-pair deletion mutation can lead to a frameshift, drastically altering the mRNA sequence's reading frame and resulting in a different amino acid sequence. Among the given options, only Option 4 correctly maintains the reading frame for the partial amino acid sequence (N-term-...P-M-N...-C-term) after the deletion, representing Proline (CCG), Methionine (AUG), and Asparagine (AAC) in that particular order.

Step-by-step explanation:

When a single base-pair deletion occurs in a gene, it may lead to a frameshift mutation, which alters the reading frame of the mRNA sequence. This can result in a completely different amino acid sequence being produced from that point onward, potentially truncating the protein or causing it to be malformed and functionally compromised.

Given the partial amino acid sequence (N-term-...P-M-N...-C-term), we can deduce this corresponds to the codons Proline (P), Methionine (M), and Asparagine (N), which are represented by the mRNA codons CCU/C, AUG, and AAU/C respectively. To find the new partial mRNA sequence corresponding to the mentioned amino acid sequence after a deletion, we consider how the deletion would affect the reading frame.

Looking at the given options, we need a sequence where a single base-pair deletion would still allow the codons to correctly encode for P, M, and N. Option 1, 5' - G | CCA | UCG | AAC | U - 3', shows the sequence after a deletion mutation, which would no longer code for the correct amino acid sequence as the reading frame is shifted. Option 2, '5 - G | CCG | UCG | AAC | U - 3', would also not fit as it would represent a reading frame with one base-pair change but no deletion. Option 3, '5 - G | CCG | ACG | AAC | U - 3', doesn’t encode the correct sequence P-M-N either, because starting from CCG, which stands for Proline, the following ACG does not correspond to Methionine (which is coded by AUG). Only Option 4, '5 - G | CCG | AUG | AAC | U - 3', provides the correct sequences for Proline (CCG), Methionine (AUG), and Asparagine (AAC) in that order, reflecting the original sequence before the deletion. Therefore, the only new partial mRNA sequence consistent with the change would be Option 4.