Video Transcript
Which of these enzymes is capable of hydrolyzing DNA? (A) Transcriptase enzyme, (B) polymerase enzyme, (C) deoxyribonuclease enzyme, (D)
ligase enzyme.
This question is asking us about enzymes that hydrolyze DNA. Hydrolysis is a chemical reaction that uses water to break a bond in a molecule. Let’s take a moment to review the structure of DNA.
Here you can see a single strand of DNA. DNA is normally made up of two strands that are twisted around each other to form a
helix shape. A strand of DNA is made up of repeating subunits called nucleotides. A nucleotide in DNA is made up of three components: a phosphate group, a deoxyribose
sugar, and a nitrogenous base. The sugar–phosphate backbone is colored in black and is indicated here.
Each nucleotide is joined together by a phosphodiester bond as shown here. When DNA is hydrolyzed, this phosphodiester bond is cleaved to leave behind a free
hydroxy group and a phosphate group. This cleaves the sugar–phosphate backbone and can produce fragments of DNA that can
be useful for different applications of biotechnology.
After reviewing the word “hydrolysis” and how it applies to DNA, we can look at each
answer to our question to see which enzyme is capable of doing this.
Answer choice (A) is incorrect because transcriptase enzymes are enzymes that form an
RNA transcript from DNA. The resulting mRNA can then be used to make proteins. This enzyme doesn’t cleave phosphodiester bonds.
Answer choice (B) is incorrect because a polymerase adds additional nucleotides to a
growing DNA or RNA strand. So this enzyme forms phosphodiester bonds and doesn’t hydrolyze them.
Answer choice (C) appears to be the correct choice because nucleases can cleave
phosphodiester bonds by hydrolysis. But before making our final decision, let’s see if we can eliminate the last
option.
Answer choice (D) is incorrect also because ligases, much like polymerases, form
phosphodiester bonds. They don’t add new nucleotides like polymerases do but instead join gaps in the
sugar–phosphate backbone that might exist in a DNA or RNA strand.
Therefore, the enzyme that is capable of hydrolyzing DNA is given by answer choice
(C), deoxyribonuclease enzyme.
