Which of the following modifications is least likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?
A) altering the nucleotide sequence of the DNA fragment
B) methylating the cytosine bases within the DNA fragment
C) increasing the length of the DNA fragment
D) decreasing the length of the DNA fragment
E) neutralizing the negative charges within the DNA fragment

Question

Quizplus · Accepted Answer

Altering the nucleotide sequence of the DNA fragment can change the size and charge of the fragment, which can affect its movement through the gel. The other options involve changes that can affect the size or charge of the fragment, and thus influence how quickly it moves through the gel. Methylating cytosines can add bulk to the bases, potentially slowing down fragment movement. Increasing the length of the DNA fragment will make it larger and hence slower, while decreasing the length will make it smaller and faster. Neutralizing the negative charges within the DNA fragment will remove the driving force behind electrophoretic movement, slowing it down.

Which of the Following Modifications Is Least Likely to Alter