Question

a section of a DNAstrandis shown. 5'-A T C G C C G A T A C T-3' which replicated DNA strand expreinced a single substitution mutation during replication
a. 3'-T A G C G G C T A T C A-5'
b. 3'-T A A G C G G C T A T G A-5'
c. 3'-T A G C G G C T A T G A T G A-5'
d. 3'-T A G G G C T A T G A

Answer 1

To determine which of the given replicated DNA strands contains a single substitution mutation, we need to compare each option to the original template strand.

The original template strand is:
5'-A T C G C C G A T A C T-3'

The corresponding complementary strand would be:
3'-T A G C G G C T A T G A-5'

Now, let's analyze the options for any single substitution mutation:

a. 3'-T A G C G G C T A T C A-5'
- This strand is mostly identical to the complementary strand but has a C substituted with an A in the last position.

b. 3'-T A A G C G G C T A T G A-5'
- In this strand, there is a substitution of T for G (the second position).

c. 3'-T A G C G G C T A T G A T G A-5'
- This strand is longer than the original and includes extra bases.

d. 3'-T A G G G C T A T G A-5'
- This strand has a substitution G for the original C in the second position and is also shorter than the predicted complementary strand.

Looking for a single substitution:
- **a** has a single substitution (C to A) compared to the correct complementary sequence.
- **b** has a substitution (G to A), but it affects two positions.
- **c** has extra bases, indicating it wouldn’t just be a substitution.
- **d** contains more than one substitution.

Thus, the strand that shows a single substitution mutation compared to the expected complementary strand is:
**a. 3'-T A G C G G C T A T C A-5'**