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 without adding or removing nucleotides
B) acetylating 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 without adding or removing nucleotides will not affect the size or charge of the DNA fragment, which are the factors that determine the movement of the fragment through the gel during electrophoresis.

All other options involve changes to the size or charge of the DNA fragment, and would therefore affect its movement through the gel. Acetylating the cytosine bases (B) would add a chemical group that could modify the charge of the DNA fragment. Increasing the length of the DNA fragment (C) would increase its size and therefore slow its movement through the gel. Decreasing the length of the DNA fragment (D) would decrease its size and therefore speed up its movement through the gel. Neutralizing the negative charges within the DNA fragment (E) would remove the charge that causes it to be attracted to the positive electrode, and would likely slow its movement through the gel.

Which of the Following Modifications Is Least Likely to Alter