Genes and Inheritance [11]: Translation (High band Biology)
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Genes and Inheritance [11]: Translation (High band Biology)

A Level Biology: Genes and Inheritance 11
– Translation Hi! Welcome to the 11th video on the series
about Genes. Today, we are going to be looking at Translation. At the end of last time, we finished off looking
at transcription. So the end-product of transcription is this single-stranded piece of genetic material
called mRNA or messenger RNA. That’s represented here by this red line. The mRNA is able to
move from the nucleus out into the cytoplasm. The reason why it needs to move to the cytoplasm
is it needs to move to this organelle called ribosome. The ribosome is actually the organelle
the builds the protein. As the mRNA moves out of the nucleus, it moves
towards the ribosome and the ribosome is represented by this blue structure here. You can see that
the mRNA has its traditional triplet code. The triplet code means the set of nucleotide
bases found in threes. Each triplet code will code for a specific amino acid. If you remember
back, there are 20 of those amino acids and so amino acids go together to form proteins. This piece of mRNA here consists of eight
triplet codes. In reality, a piece of mRNA can consist of several thousand triplet codes. Either end of the mRNA code has a start codon
and stop codon and the start codon tells the ribosome to start reading from and the stop
codon indicates where it needs to stop. It is also the end of the code for the protein. There is this other molecule that we have
up here call transfer RNA. Now, what that is going to do is that has a very specific
code. This transfer RNA is a very specific code. In this case, UAC and because the nucleotide
base is bind up in very, very specific ways and so in this instance, U will bind with
A, A will bind with U and C will bind with G. Hence why the shape of these bases will
fit the shape of these bases and hence they’ll fit together. This triplet code is known as
the anticodon. This triplet base is known as the codon and so they will bind. This transfer
RNA has an anticodon of UAC. A transfer RNA that has UAC will always code for the same
type of amino acid, one of the 20 that it could possibly code for. Then the next thing
that will happen is another transfer RNA molecule, however this time this has got GGG anticodon
and because G binds with C, it is complementary shape to this codon and it will come in here
and bind. You probably realize from before that a protein
is several amino acids joined together. In order for this to become a protein, the two
amino acids needs to join up and this is what happens. This bond that happens between amino
acids forms between these two and is referred to as a peptide bond. The next thing that
would happen is this transfer RNA here is now free to move away. It has done its job.
It has brought the correct amino acid in and it is now free to move away, leaving behind
the other amino acid and that can then go off to pick up the specific type of amino
acid here aa1. You then get the ribosome moving along and so it is going along to read the
code. Now, it is looking for a transfer RNA that has anticodon of CCC, hence this one
in here because it is there for the complementary shape with the code on and it comes in and
it binds. Again, the same thing happens, amino acid
2 and amino acid 3 need to join up and therefore, you get a peptide bond being formed between
those two. This continues all the way down to the bottom end of the mRNA until it reaches
the stop codon. So what you’re left with is the complete protein, this one consisting
of eight amino acids and then it is then free to go off to do whatever function that is,
whether that is an enzyme, used to catalyse a reaction or whatever that’s used to form
some form of tissue. In summary, the first thing that happens in
translation is the mRNA leaves the nucleus and moves towards the ribosome in the cytoplasm.
The ribosome then enables transfer RNA or specific transfer RNA to bind the mRNA and
it binds to the triplet code and the transfer RNA also has something that is referred to
as an anticodon which is a triplet code. That transfer RNA, along with its anticodon, brings
with it a specific amino acid. The ribosome continues to move down into the mRNA, bringing
in the correct transfer RNA and therefore, the correct amino acid. Those amino acids
join up and form a peptide bond and this continues to happen until the ribosome reaches a section
of the mRNA that codes for a stop. Hence, the protein is made and then it can be used. [end of audio – 05:33]
A Level Biology: Genes and Inheritance 11 – Translation

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