DNA Technology IMAT 2014

A circular bacterial plasmid consists of 1000 base pairs (bp). A specific restriction enzyme has three recognition sites within this plasmid.

The sites are at 150 bp, 250 bp and 950 bp. After complete restriction, what size are the fragments?

A 100 bp, 200 bp and 700 bp only

B 100 bp, 150 bp, 200 bp only

C 50 bp, 100 bp, 150 bp and 700 bp only

D 50 bp, 100 bp and 700 bp only

E 50 bp, 100 bp, 150 bp, 200 bp and 700 bp

why is the answer A and not E

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So since it is a plasmid, we must remember it is circular. The two ends of 50 and 150 bp join together to make 200 bp. Does this make sense? Here’s a diagram to help!

Imgur

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ohhh ok, yeah that makes sense ! thanks heaps :slight_smile: