Video Transcript
A simple diagram of the structure
of DNA is provided. What part of this structure is
indicated by label X?
You’re probably familiar with the
double-stranded helix structure of DNA. An untwisted representation of the
molecule is shown here. You could see the two strands
indicated here. Each strand is made up of repeating
subunits called nucleotides. A single nucleotide is made up of
three different parts: a phosphate group, a deoxyribose sugar, and a nitrogenous
base. There are four different bases in
DNA: guanine, represented in orange; cytosine, represented in blue; adenine,
represented in green; and thymine, represented in pink.
As you can see here, the two
nitrogenous bases can form hydrogen bonds with each other and pair up. This is how the two strands are
held together. Each nucleotide is attached to the
next by a phosphodiester bond. Through this phosphodiester bond, a
phosphate group of one nucleotide is bonded to the sugar group of the next. This forms the sugar–phosphate
backbone of one strand.
Therefore, the part of this diagram
that is labeled as X is the sugar–phosphate backbone.
