Two circular DNAs are isolated,both with 1000 bp,are electrophoresed side-by-side:
#1: twist (T)= +100,writhing number (W)= −5
#2: twist (T)= +1000,writhing number (W)= +5
A)DNA #1 should migrate further.
B)DNA #2 should migrate further.
C)They should migrate the same distance.
D)More information is required to determine.
E)This cannot be determined regardless of additional information.

Question

Quizplus · Accepted Answer

The linking number is the sum of the twist and writhing numbers. The linking number is a topological invariant, meaning that it cannot be changed without breaking the DNA. Therefore, the two DNAs have the same linking number, and they will migrate the same distance during electrophoresis.

Two Circular DNAs Are Isolated,both with 1000 Bp,are Electrophoresed Side-By-Side