Your friend has cut a 3000-nucleotide-pair circular plasmid with either or both restriction enzymes A and B, and has separated the digestion products by electrophoresis. The results are shown in the schematic drawing below, with the approximate size of the fragments indicated above each band. Based on these results, what is the closest distance (in nucleotide pairs) between an A restriction site and a B restriction site on this plasmid?
A) 400
B) 600
C) 1000
D) 1200
E) 1600

Question

Your friend has cut a 3000-nucleotide-pair circular plasmid with either or both restriction enzymes A and B, and has separated the digestion products by electrophoresis. The results are shown in the schematic drawing below, with the approximate size of the fragments indicated above each band. Based on these results, what is the closest distance (in nucleotide pairs) between an A restriction site and a B restriction site on this plasmid? 
A) 400 
B) 600 
C) 1000 
D) 1200 
E) 1600

Quizplus · Accepted Answer

One of the B sites is 1000 nucleotide pairs away from the A site, and the second B site is another 400 nucleotide pairs further, making it 1400 nucleotide pairs away in one direction and 1600 nucleotide pairs away in the other direction around the circular plasmid.

Your Friend Has Cut a 3000-Nucleotide-Pair Circular Plasmid with Either