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Sometimes it feels like DNA gets all the credit.
Yes, the structure DNA is amazing.
It has a beautiful double helix structure!
A twisted ladder!
It has its own emoji!
DNA stores genetic information and codes for your traits.
However, sometimes what gets left out is how important RNA is.
Without RNA, you actually couldn’t get that genetic message out to your cells so that
they can start producing proteins.
We talk about this in protein synthesis.
RNA is a very important biomolecule – just as important as DNA.
In fact, RNA is even hypothesized as coming first before DNA in the RNA World hypothesis---something
we need to make a separate video about.
So let’s compare and contrast DNA with RNA.
First you will find DNA and RNA in all living organisms.
In eukaryotic cells, DNA tends to be found in the nucleus while you can find RNA both
in and out of the nucleus.
Prokaryotic cells don’t have a nucleus.
Both DNA and RNA are nucleic acids, which are a type of biomolecule.
Nucleic acids have a monomer---which if you remember from our biomolecules video, a monomer
is a building block.
The monomer for nucleic acids is a nucleotide so both DNA and RNA have nucleotides.
The nucleotides of both RNA and DNA have three parts: a phosphate, sugar, and a base.
Let’s draw 6 nucleotides of DNA and 6 nucleotides of RNA.
DNA is generally double stranded, and if focusing on these two strands of nucleotides here,
you can see they run antiparallel to each other.
RNA is generally single-stranded so you are just seeing one strand here.
The sugar in DNA is deoxyribose and the sugar in RNA is ribose.
This makes sense because DNA stands for deoxyribonucleic acid.
That’s helpful to know because the “deoxyribose” is a sugar, and “nucleic acid” is that
type of biomolecule it is.
RNA stands for ribonucleic acid as its sugar is ribose.
The bases in DNA are adenine, thymine, guanine, and cytosine.
It helps to remember the popular mnemonic device: apples in the tree (that helps you
remember that A goes with T) and car in the garage (so C goes with G) to understand how
DNA bases pair.
The bases in RNA are adenine, uracil, guanine, and cytosine.
Notice the different one?
It’s uracil!
So you have to change that popular mnemonic device here…instead of apples in the tree…maybe
the apples are…under?
Car in the garage still works.
We mentioned earlier that DNA codes for your traits, but it couldn’t do that without
RNA’s help.
In our protein synthesis video, we talk about three different types of RNA and their very
important roles.
mRNA, which stands for messenger RNA. mRNA’s job is to carry a message based off of the
DNA.
In eukaryotic cells, DNA generally stays in the nucleus but mRNA has the ability to leave
the nucleus to take this message to a ribosome.
Ribosomes make protein and RNA is actually a major component of ribosomes.
This type of RNA is called rRNA, which stands for ribosomal RNA.
Finally, we discuss transfer RNA or abbreviated tRNA.
Its job is to transfer amino acids to match the correct mRNA codon.
Codon charts using mRNA codons have been developed so that you can actually see which amino acid
is brought for each mRNA codon.
When those amino acids are joined together, they make a polypeptide chain.
Proteins are made of one or more of these polypeptide chains, and proteins have tons
of different roles.
But we don’t want to spoil it---check out more in our protein synthesis video.
Before we go, let’s try a little 3 question quiz shall we?
Just pause it after the question so you have time to think about it!
Question 1) If I have 8 DNA nucleotides, how many DNA bases do I have?
How many base pairs?
The answer: Each nucleotide---regardless of whether it’s a DNA or RNA nucleotide---
has a phosphate, sugar, and a base.
So 8 DNA nucleotides would have 8 bases.
DNA bases pair like this- and that’s 4 DNA base pairs.
Question 2) If one strand of DNA has these bases shown here--- A, T, T, G, A, C--- can
you complete what the complementary DNA bases would be for the other DNA strand?
The answer: So remember those base pairing rules for DNA and the popular mnemonic.
If placing the bases in this image, reading in the direction shown on this image, they’d
be T, A, A, C, T, G.
Question 3) In a process known as transcription, a complementary RNA strand called messenger
RNA has to complement the DNA.
More about that in our protein synthesis video.
So if I still had that original portion of DNA here, what would the complementary RNA
bases here be?
The answer: So remember it’s asking for RNA.
No thymine here; it’s uracil instead.
Apples under helps you remember A with U.
Car in the garage helps you remember C with G.
So in this portion, reading in the direction shown on this image, we’d have these RNA
bases.
Notice the answer is similar to the last answer, but there are uracil bases here instead of
thymine.
One last thing.
Our models here--- they’re unable to show the beautiful 3D shape, the exact number of
bases per turn, the chirality---but we’ve left you some links to explore because the
goal of our videos is always to introduce topics so you can discover all the fascinating
details and exceptions.
Check out our further reading description to keep that curiosity going.
Well, that’s it for the Amoeba Sisters and we remind you to stay curious.