A student digests a 6,000-bp plasmid with three restriction enzymes separately and runs the products on a gel. EcoRI cuts the plasmid once, producing one band. BamHI produces two bands at 4,000 and 2,000 bp. EcoRI + BamHI double digest produces three bands at 3,500, 1,500, and 1,000 bp.
How many BamHI sites does the plasmid have?
- A
Three
- B
Zero
- C
One
- Dcheck_circle
Two
Explanation
A circular plasmid cut into n fragments has n cut sites. BamHI alone gives two fragments, so the plasmid has two BamHI sites.