Question

Consider an experiment in which nucleic acids are separated using agarose gel electrophoresis. In the gel you load the following samples: Lane 1: a population of linearized 3000-bp double-stranded DNA (dsDNA) molecules. Lane 2: a population of circular 3000-bp double-stranded DNA (dsDNA) molecules. Lane 2: a population of circular 3000-bp double-stranded DNA (dsDNA) molecules Which population of nucleic acids would most likely migrate through the gel fastest, and in which direction through the gel will these molecules migrate?

a. The linearized dsDNA would most likely migrate faster than the circular dsDNA. All DNA molecules would migrate toward the positive end of the gel.
b. The circular dsDNA would most likely migrate faster than the linearized dsDNA. All DNA molecules would migrate toward the positive end of the gel.
c. The circular dsDNA would most likely migrate faster than the linearized dsDNA. All DNA molecules would migrate toward the negative end of the gel.
d. The linearized dsDNA would most likely migrate faster than the circular dsDNA. All DNA molecules would migrate towards the negative end of the gel.

Answer 1

a. The linearized dsDNA would most likely migrate faster than the circular dsDNA. All DNA molecules would migrate toward the positive end of the gel.

Step-by-step explanation:

Electrophoresis gel is a technique widely used in molecular biology in order to separate macromolecules (e.g., DNA, RNA, proteins) according to their size and charge. The DNA is a molecule negatively charged, thereby the DNA fragments will always move toward the positive electrode in an electrophoresis gel. In the DNA molecule, the charge-to-mass ratio remains constant, thereby DNA fragments will separate based on their size (i.e., small DNA fragments will move through the gel faster than large ones). Moreover, for the same size, linear dsDNA fragments experience less frictional resistance against the gel than circular dsDNA fragments and, therefore, linearized dsDNAs run faster.