Video Transcript
Between which DNA bases do two
hydrogen bonds form? (A) C and G, (B) C and A, (C) G and
T, (D) A and T, (E) C and T.
DNA is a biological macromolecule
that carries genetic information. It is made up of two strands that
wrap around each other to form a double-helix shape as we can see here. Let’s zoom in so we can get a
better look at its chemical structure to answer this question.
Here you can see a segment of DNA
with its two strands indicated. Each strand is made up of repeating
subunits called nucleotides. There are three parts to a
nucleotide: a phosphate group, a deoxyribose sugar, and a nitrogenous base. In DNA, there are four nitrogenous
bases: guanine, shown in orange; cytosine, shown in blue; adenine, shown in green;
and thymine, shown in pink.
The nitrogenous base from one
strand can pair with the nitrogenous base on the opposing strand to form a base
pair. These bases can pair because they
form hydrogen bonds with each other, represented here by the black dots between the
bases. As you can see, guanine can pair
with cytosine using three hydrogen bonds. And adenine can pair with thymine
using two hydrogen bonds.
Therefore, the DNA bases that form
two hydrogen bonds are given by answer choice (D), A and T.
