Video Transcript
In the process of DNA
replication, what is the primary role of DNA helicase? (A) DNA helicase detects and
repairs any errors that are made by incorrect base pairings during DNA
replication. (B) DNA helicase breaks the
hydrogen bonds between base pairs, separating the two strands of DNA. (C) DNA helicase forms
phosphodiester bonds between nucleotides to form a strand of DNA. (D) DNA helicase adds
nucleotides to a growing DNA chain, synthesizing a strand of DNA complementary
to the template strand. Or (E) DNA helicase joins the
gaps in the backbone between newly formed DNA fragments.
This question is asking us what
the primary role of the enzyme DNA helicase is during DNA replication. To answer this, let’s first
clear the answer choices so we have more room to work with. In order for a cell to divide
and make a new cell, its DNA must first be copied or replicated to form a new
molecule of DNA. You’ll recall that DNA is a
double-stranded helix. These colored boxes that you
see are the different nucleotides that make up the DNA molecule.
Let’s zoom in here so we can
take a closer look. Here, we can see the two
strands of DNA. DNA is made up of repeating
subunits called nucleotides. Each nucleotide contains a
phosphate group, a deoxyribose sugar, and a nitrogenous base. In DNA, there’s four types of
nitrogenous bases: guanine, cytosine, adenine, and thymine. The sequence of these
nitrogenous bases along these strands of DNA can code for different genes. These bases form base pairs
because complementary bases can hydrogen-bond with each other. Guanine always pairs with
cytosine and forms three hydrogen bonds, while adenine always pairs with thymine
and forms two hydrogen bonds. These hydrogen bonds between
these bases are what hold these two strands of DNA together.
In order for DNA replication to
occur, these two strands need to be separated so the DNA can be copied. The enzyme that breaks these
hydrogen bonds and separates the two strands is called DNA helicase. Therefore, in the process of
DNA replication, the primary role of DNA helicase is to break the hydrogen bonds
between base pairs separating the two strands of DNA.
