genetic control of protein function


Genetic code

The Main Features Of The Genetic Code:

Each amino acid in a protein is coded for by a sequence of three nucleotide bases on mRNA

A few amino acids have only a single codon 

The code is degerate- most amino acids are coded for by more than one codon

Some codons are stop codons which end the polypeptide chains

The code is non-overlapping- each sequence is only read once 

It is a universal code- the same codon codes for the same amino acid in all organisms

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Messenger RNA

Messenger RNA (mRNA)

consists of thousands of nucleotides

long single stranded helix 

It is manufactured when DNA forms a mirror of part of one of its two strands 

mRNA leaves the nucleus via pores in the nuclear envelope and enter the cytoplasm, where it associates with the ribosomes

acts as a template for proteins to be built 

its structure is suited to its fuctions because it posseses the correct sequencess of the  triplets of the organic bases that code for specific plypeptides 

it is ealiy broken down and exists only while it is needed to manufacture a given protein

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Transfer RNA

Tranfer RNA (TRNA)

small molecule- made up of around 80 nucleotides

It is a single-stranded chain folded into a clover leaf shape, whith one end of the chain extending beyond the other- which amino acids can attach to 

There are several types of tRNA 

At the end of the tRNA molecule is a sequence of three other organic bases called antcodons- for each amino acid their is a differnt sequence of organic bases on the anticodon 

During protein synthesis, the anticodon pairs with the three complementary organic bases that makes up triplet of bases on mRNA 

The tRNA structure is suited to its role of lining up amino acids on the mRNA template during protein synthesis

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