The restriction enzyme BamHI cleaves the sequence 5′-GGATCC-3′ between the two Gs. Following cleavage, the single stranded overhang consists of which of the following bases? A. GGATCC B. GATCC C. GATC D. ATCC BamH | 5′-GGATCC-3
The Correct Answer and Explanation is:
The correct answer is C. GATC.
Explanation:
BamHI is a type II restriction enzyme that specifically recognizes and cleaves the DNA sequence 5′-GGATCC-3′. This enzyme cuts between the two G bases in the sequence, resulting in single-stranded overhangs known as “sticky ends.”
The recognition and cutting pattern for BamHI is as follows:
- The enzyme cuts between the two Gs in the sequence 5′-GGATCC-3′, meaning it cleaves the bond between the first G and A (on the top strand) and the second G and C (on the bottom strand).
- After cleavage, the top strand will end with the sequence 5′-G (at the cut site), and the bottom strand will end with 3′-C (at the cut site).
Thus, the sticky end or single-stranded overhang left after cleavage will be the part of the sequence GATC, as the second strand will have a complementary overhang after the cut.
This overhang is crucial for ligation with other DNA molecules that have compatible sticky ends. The presence of complementary overhangs allows the ends of two DNA fragments to be joined together by DNA ligase.
To summarize:
- BamHI cleaves 5′-GGATCC-3′ between the two Gs.
- The resulting overhang on the top strand is GATC.
- Therefore, C. GATC is the correct answer.
