Question

The chain termination method of sequencing:

a. uses labeled ddNTPs
b. uses only dideoxynucleotides
c. uses only deoxynucleotides

d. uses labeled dNTPs

Short answer

option a is correct.

Step-by-step solution

Introduction

The basic sequencing technique used in all modern day sequencing projects is the chain termination method (also known as the dideoxy method), which Fred Sanger developed in the 1970s. The chain termination method involves DNA replication of a single- stranded template by using a primer and a regular deoxynucleotide (dNTP), which is a monomer, or a single DNA unit.

Explanation for correct option

Chain termination method method of DNA sequencing using labeled dideoxynucleotides to terminate DNA replication; it is also called the dideoxy method or the Sanger method . Thus option a is correct.

Explanation for incorrect options 

b. uses only dideoxynucleotides is wrong as the ddNTPs are labeled and mixed with some amount of primer and dNTPs
c. The primer and dNTP mix with a small proportion of fluorescently labeled dideoxynucleotides (ddNTPs)

d. Labelled dNTPs are not used