Question

Which statement about Sanger sequencing is false?

(A) Because a dideoxynucleotide lacks the 3'-hydroxyl group, the next nucleotide cannot be added, and therefore DNA synthesis is blocked at the point of addition.
(B) Four different arrays of labeled DNA chains increasing in length by one base are produced.
(C) If the tag is a fluorescent dye and a different fluorescent color emitter is used for each of the four ddNTP reactions, then the four reactions can take place in the same test tube and the four sets of nested DNA chains can undergo electrophoresis together.
(D) To read the DNA sequence of the synthesized strand in the 5'-to-3' direction, the gel is read from top to bottom.

Answer 1

Answer:

D) To read the DNA sequence of the synthesized strand in the 5'-to-3' direction, the gel is read from top to bottom.

Explanation:

The DNA sequence of the synthesized strand in the 5'-to-3' direction is read from the bottom to the top. On the electrophoresis gel, bands corresponding to the smallest DNA fragment migrate to the bottom of the gel.  Meaning, the DNA primer fragment would be at the bottom and immediately above it would be the fragment that had fewer dNTPs (deoxynucleotidetriphosphates) incorporated prior elongation termination by an incorporated ddNTP.