During dna replication,the enzyme dna helo case function to
a)unzips and unwind the strand of dna.
b)match the correct base
c) rejoin the hydrogen bonds

Alright, so DNA sequencing is the process of determining the sequence of nucleotides, or basically the order of them. The nucleotides are adenine, guanine, cytosine, and thymine, AKA: (As, Gs, Cs, and Ts)

Let me explain: All strands of DNA have a specific construction of nucleotides, which basically form the structural unit of DNA.

DNA sequencing is a process of identifying those nucleotides and how their composition is. It's determined through the use of various methods and technologies. 

If you've ever seen a chart involving dozens of C's, T's, A's, and G's, then that's a model of the nucleotides. 

~Hope this helps!