Question

The DNA sequence CCAAGAAGTCGACAAACA is translated to synthesise the

amino acid chain gly-ser-ser-ala-val-cys.
As a result of a mutation, the sequence length of the amino acid chain is shortened from six to two amino acids. A stop codon in mRNA is UGA.

Which base in the DNA sequence was changed by the mutation?

A. A
B. C
C. G
D. T

Answer 1

option c "G"

Step-by-step explanation:

Answer 2

G

Step-by-step explanation:

your have to look at the second triplet of bases: AGT since it says the chain is only 2 amino acids long (so the 3rd triplet must be the stop codon).

Now remember that for the DNA-mRNA transcription A becomes U, T becomes A, C becomes G and vice versa. So to codify a UGA codon you need ACT in the DNA. Since we have AGT instead, it means the G was changed by the mutation.