Captions are on! Click CC at bottom right to turn off. 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.
