Question

The molecular weight marker is an example of a  ["Positive" OR "Negative"] control. Which would it be?

In relation to this what would be the the main goal of loading dye in gel electrophoresis?

A. To make the reaction run faster.

B. It is a positive control.

C. To measure the base pair size of the DNA fragments.

D. To weigh down the samples.

Its either A or C correct but which one between the two im confused?

Answer 1

DNA ladder with respect to the gel electrophoresis is a positive control, because the DNA ladder contains DNA fragments, the presence or absence of bands in the ladder helps us to find out whether we did any mistakes during the gel making or connecting the gel to the electric supply, DNA is negatively charged so the wells have to be close to the negative electrode so that the DNA fragments can move through the gel towards positive electrode, and if the concentration of the gel is very less and if the gel is overrun we cannot find any bands in the ladder. so the DNA ladder is a positive control.

  DNA ladder consists of DNA fragments of different lengths, the distance migrated through the gel depends on the length of the DNA fragments, larger DNA molecules migrate slowly and smaller fragments migrate faster, distance moved along the gel depends on the concentration of the gel, so the DNA ladder is used to determine the size of the fragments in the gel.

C. To measure the base pair size of the DNA fragments.