Correct option is C
The correct option is (c). The explanation is as follows-
Step 1: Forward primer
The forward primer must anneal to the start of the target region on the sense strand, or just upstream of it.
The sequence just before the uppercase region is:
gagatcaggactta
The last 8 bases before the target: aggactta (5′→3′).
So forward primer: 5′ - AGGACTTA - 3′
Step 2: Reverse primer
The reverse primer must anneal to the complement of the sequence downstream of the target region — i.e., on the antisense strand, near the 3′ end of the target region.
Downstream sequence: ggccaagtc (5′→3′).
To find the reverse primer, take the reverse complement of the downstream sequence.
Calculating reverse complement of ggccaagtc:
Sequence: 5′ - G G C C A A G T C - 3′
Reverse: 3′ - C T G A A C C G G - 5′
Complement (reading 5′ to 3′):
C → G
T → A
G → C
A → T
A → T
C → G
C → G
G → C
So reverse complement (5′→3′) is: 5′ - ACTTGGCC - 3′
