Question

The amino acids in the original partial sequence (N-term-...P-I-E...-C-term) have little to no impact on protein structure and function. However the amino acid sequence near the C-terminal end of the protein is required for normal function. Any amino acid changes in this region of the protein will result in a nonfunctional protein. Given this information, which reversion mutation in the gene would restore the normal function of the protein?

a. Insertion of 2 base-pairs in the region of the proline codon
b. Deletion of 5 base-pairs in the region of the proline codon
c. Deletion of 2 base-pairs in the region of the proline codon
d. Deletion of 1 base-pair in the region of the proline codon
e. Insertion of 1 base-pair in the region of the proline codon
f. Insertion of 4 base-pairs in the region of the proline codon

Answer 1

To restore normal protein function, a reversion mutation must not cause a frameshift. An insertion of a multiple of three base pairs is needed as it maintains the reading frame intact. The insertion of four base pairs (option f) might not affect the C-terminal sequence and is the closest to a likely correct choice.

Step-by-step explanation:

To restore the normal function of the protein with a reversion mutation, we must reverse the effects of the initial mutation without causing additional disruptions in protein coding. Given that amino acid changes near the C-terminal end are critical for protein function, any insertion or deletion that doesn't affect this region can be considered. More specifically, it's crucial that the number of base pairs inserted or deleted is a multiple of three—otherwise, it would lead to a frameshift mutation, resulting in a nonfunctional protein. Since none of the options directly address changes at the C-terminal end, we must consider which mutation will not cause a frameshift.

Insertions or deletions that are not multiples of three lead to frameshift mutations, altering the reading frame and resulting in incorrect amino acids being incorporated from the point of mutation forward, often creating a nonfunctional protein. Therefore, we can eliminate options that suggest adding or removing one or two base pairs (a, c, d, e), as they will cause frameshift mutations. Inserting or deleting multiples of three keeps the reading frame intact. However, since the question prompts us to restore normal function through a reversion mutation and there is no information suggesting an initial frameshift, the best answer would be the insertion of three base pairs, but it's not provided among the choices. Thus, we should choose the closest option, which would be to insert or delete a number of base pairs not affecting the critical C-terminal sequence—option f, which suggests an insertion of four base pairs, is the only remaining possibility that might not affect the critical C-terminal sequence.

Answer 2

OPTIONS : B,C,E,F

Step-by-step explanation:

The Reversion mutation in the gene that would restore the normal function of the protein :

All the options given can restore the normal function except options : A and D

For Deletion of 5 base-pairs in the region of the proline codon

Normal sequence 5' - G | CCG | AUC | GAA | CU - 3' while the mutated sequence is : 5' - G | CCG | AUG | AAC | U - 3' . this shows that the removal of the 5 case pairs will only remove 2 amino acids restoring the normal protein in the process and not affect the C terminal of the amino acids and also the reading frame will be restored

normal protein.

For Deletion of 2 base-pairs in the region of the proline codon

The Normal sequence 5' - G | CCG | AUC | GAA | CU - 3' while Mutated sequence 5' - G | CCG | AUG | AAC | U - 3'

This shows that the deleted base pair is from this codon hence removing the two base pairs will lead to the reading frame been restored and also the C terminal amino acids, but this will result to a protein with a less than one amino acid