As we know a gene is a section of DNA which codes for a protein, but what is a protein?
A protein is just a long chain of amino acids.
Its the order of these amino acids, which create the diverse range of proteins our cells produce.
An amino acid is a building block of proteins, just as a nucleotide is a building block of DNA.
However, unlike a nucleotide there are 20 types of amino acids. How can 4 bases code for 20 amino acids?
If one base = 1 amino acid, there could only be 4 amino acids. If 2 bases made one amino acid there could only be 16.
It was Crick who worked out there must be 3 bases.
These 3 nucleotides in a sequence are called a triplet code.
We can combine the 4 bases, to create 64 triplet code. This means, there is more than one triplet for an amino acid. This means the genetic code is degenerate, or redundant, because more than one triplet codes for an amino acid.
As well as stop and start codes for the DNA.
Creating a protein requires a few steps
We can break protein synthesis into 2 processes
Transcription and Translation
First things first you have to unzip the DNA.
This mean the two strands are broken up.
We know that DNA is very important to our cells, so we can’t risk damaging it.
So our cells copy DNA into mRNA (messenger RNA).
mRNA is single stranded, and instead of using Thymine (T), it uses Uracil (U).
The mRNA moves out of the nucleus through the pores. As it leave it finds a ribosome, and the ribosome attaches to it.
The ribosome begins to read the mRNA.
tRNA brings amino acids to the ribosome. As we said before a codon on mRNA is 3 nucleotides long. The anti codon on tRNA is the opposite sequence to the mRNA.
Each tRNA has a specific anti-codon sequence and a specific amino acid.
Once the ribosome gets to a stop codon, it breaks apart and releases the mRNA.
