The final step in a DNA sequencing reaction is to run the DNA fragments on a gel. What purpose does this serve?
A) It terminates the sequencing reaction at particular bases.
B) It provides the substrate for DNA polymerase.
C) It separates dideoxynucleotides from deoxynucleotides.
D) It separates DNA fragments generated during the sequencing reaction based on one- nucleotide differences in their size.

Question

Quizplus · Accepted Answer

Running the DNA fragments on a gel separates them based on their size, with smaller fragments moving farther down the gel than larger fragments. Since each termination reaction during DNA sequencing generates fragments of different sizes based on where the dideoxynucleotide was incorporated, the gel electrophoresis step allows us to separate the fragments based on their size and determine the sequence by reading the pattern of bands on the gel.

The Final Step in a DNA Sequencing Reaction Is to Run