Video Transcript
DNA and RNA are both examples of
nucleic acids. Compare and contrast the structures
of DNA and RNA.
This question is asking us to
compare, which is to describe similarities, and to contrast, which is to describe
differences. And they want us to describe the
similarities and the differences between the structures of DNA and RNA. And we’re being asked to
specifically focus on the structure or the parts and not the function or what it is
these molecules do.
One way to organize your
information when you’re working on a compare-and-contrast question is to make a
table with a column for DNA, a column for RNA, and a column for both. Then you simply fill in whatever
you know which will help you to write out your answer. Another way to organize your
information is to make a Venn diagram with a circle for DNA, a circle for RNA, and
information about both where the two circles overlap. I like a more visual approach, so
I’m going to continue with the Venn diagram, but you can choose to use whichever
method is most comfortable for you. I’ve also added some visual clues
which we’ll annotate together before writing out our final answer.
Let’s start by noting that this
question already told us that DNA and RNA are both nucleic acids. And we know that nucleic acids are
polymers and that a polymer is a large molecule made up of repeating subunits, which
we call monomers. The monomers of nucleic acids are
called nucleotides, and each nucleotide is made up of a phosphate group, a pentose
sugar, and a nitrogen-containing base. However, DNA is made of two strands
of nucleic acids bonded together into a double helix, while RNA is typically a
single-stranded molecule.
There are also some differences
between the nucleotides of DNA and RNA. The pentose sugar in the
nucleotides of DNA is deoxyribose sugar, while in RNA it’s ribose sugar. Also the bases in DNA are adenine,
thymine, cytosine, and guanine. RNA molecules possess adenine,
guanine, and cytosine, but the base thymine is replaced by the base uracil. Now that we’ve summarized the
similarities and differences in the structure of DNA and RNA in our Venn diagram,
we’re ready to write out our answer. Your answer, of course, will be
written in your own words, but it should look something like this.
Both DNA and RNA are polymers
formed from multiple subunits called nucleotides. DNA and RNA nucleotides are both
formed from a pentose sugar, a phosphate group, and a nitrogenous base. However, the pentose sugar in DNA
is deoxyribose, and in RNA it is ribose. The nitrogenous bases in DNA are
adenine, thymine, cytosine, and guanine, but in RNA thymine is replaced by
uracil. DNA also forms a double-stranded
molecule, whereas RNA forms single-stranded molecules.
