hown below is a portion of a wild-type DNA sequence that encodes the last amino

Question

hown below is a portion of a wild-type DNA sequence that encodes the last amino acids of a protein that is 270 amino acids long. The first three bolded base pairs indicate the frame and include the coding region.

5'...GCTAAGTATTGCTCAAGATTAGGATGATAAATAACTGG3'

3'...CGATTCATAACGAGTTCTAATCCTACTATTTATTGACC5'

A change of one base pair leads to the protein increasing in length by oneamino acid. With respect to the sequence given above, which base pair would you change, and what would you change this base pair to for the protein to increase in length by one amino acid.

Explanation / Answer

Ans. is a Frameshift Mutation.

Given,

5'...GCTAAGTATTGCTCAAGATTAGGATGATAAATAACTGG 3'

3'...CGATTCATAACGAGTTCTAATCCTACTATTTATTGACC 5'

Now FrameShift Mutation (is either insertions or deletions)
But since we wan't an Increase in length of amino acids, we consider here an Insertion.

Now an Insertion can be any where, which leads to change in Frame of Reference if occurs in middle of the given sequence

Consider, (I've indicated an Insertion here in BOLD letters and in inverted commas)

5'...GCTAAGTATTGCTCAAGATTAGG"G"ATGATAAATAACTGG 3'

3'...CGATTCATAACGAGTTCTAATCC"C"TACTATTTATTGACC 5'

Now this leads to increase in Length of protein by 1 amino acid and frame of reference is changed from the point of Insertion.
The Insertion should be such that the change in Frame of Reference should not bring any STOP codons.

Hope you Understand from this. If any Doubts still please Ask.

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