Original DNA: TAC CTA GGA CCA ACT has changed to TAC CTA GAC CAA CT.

Question

What type of mutation has occurred, and has it caused a frameshift?

a
insertion - no
b
translocation - yes
c
substitution- no
d
deletion - yes

Answer 1

The original DNA sequence is:

TAC CTA GGA CCA ACT

The modified sequence is:

TAC CTA GAC CAA CT

To analyze the changes:

1. Compare the sequences:

   • At positions 7-9, "GGA" has changed to "GAC" (the second codon).
   • At positions 10-12, "CCA" has changed to "CAA".

2. The change in "GGA" to "GAC" is a substitution because one nucleotide (G) has been replaced with another (A).

3. The change in "CCA" to "CAA" is also a substitution.

Since there are no insertions (addition of nucleotides) or deletions (removal of nucleotides), these changes are not causing a frameshift, as the reading frame of the rest of the sequence remains intact.

Thus, the correct answer is:

c. substitution - no