Video Transcript
A list of bonds found in biological
molecules is provided. Which of these bonds is found
between adjacent nucleotides in a DNA double helix? (1) Hydrogen, (2) peptide, (3)
phosphodiester, (4) ionic, (5) glycosidic.
This question is asking us about
the type of bond found in DNA, so let’s discuss the structure of DNA in some
detail. DNA is made up of two strands that
coil around each other in a double-helix shape. Here we can see the chemical
structure of DNA with the two strands indicated. Each strand is made up of repeating
subunits called nucleotides. Each nucleotide is made up of three
parts: a phosphate group, a pentose sugar — in DNA, this pentose sugar is called
deoxyribose — and a nitrogenous base. In DNA, there’s four nitrogenous
bases: guanine, or G for short, cytosine, adenine, and thymine. These nitrogenous bases can
base-pair with each other by forming hydrogen bonds. This is what holds the two strands
of DNA together.
Nucleotides are joined together by
bonds called phosphodiester bonds. This bond includes the phosphate
group as well as the two attached carbons. Going back to our question, the
name of the bond that joins adjacent nucleotides is called a phosphodiester
bond.