Scientists can determine the size of DNA fragments through a process known as gel electrophoresis. In this process, DNA is loaded into a gel submerged in a liquid solution through which an electric current is run. Large DNA molecules move slower and can be observed at the top of the gel, whereas smaller DNA fragments move faster and are seen at the bottom of the gel. Based on what you know about the properties of DNA, how is the electric current arranged in this process?
A)Since DNA is negatively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel.
B)Since DNA is negatively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel.
C)Since DNA is positively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel.
D)Since DNA is positively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel.
E)Since DNA is uncharged, the placement of the positive end and negative end does not matter.

Question

Quizplus · Accepted Answer

DNA is negatively charged due to its phosphate backbone. Therefore, to move DNA fragments through the gel, the positive end is placed at the bottom to attract the negatively charged DNA molecules downwards through the gel.

Scientists Can Determine the Size of DNA Fragments Through a Process