Question

What is the role of a primer in DNA replication? What would happen if you forgot to add a primer in a tube containing the reaction mix for a DNA sequencing reaction?

Short answer

Primer gives DNA pol a 3'-OH group so it can begin adding nucleotides. Without a primer, there wouldn't be any reaction in the tube and no bands would show up on the electrophoresis.

Step-by-step solution

Introduction 

One of the DNA (deoxyribonucleic acid) strands serves as the template strand during DNA replication, which is the process of reproducing DNA. All living things, including those with DNA as their genetic material, go through this biological process. To create a new strand, in addition to the template strand, various proteins and enzymes are needed.

The explanation for the answer. 

A primer is a brief polynucleotide segment that aids DNA polymerase in starting its work and primes, or prepares, the way for DNA replication. The primer is known as an RNA primer since it is comprised of RNA. Without a primer, there wouldn't be any reaction in the tube and no bands would show up on the electrophoresis.