DNA RNA

Sequence of nuceltides in DNA forms a code that determins the sequence of amino acids in the protiens of an organism 

In eukaryotic cells, the DNA is stored in the nucleus.

However, synthesis of protiens takes place in the ribosomes in cytoplam. 

So, the DNA code needs to be transcribed to a single-stranded molecule called RNA.

mRNA - transfers the DNA code from the nucleus to the cytoplam.

mRNA is small enough to leave the nucleus through nuclear pores in the envelope and to enter the cytoplam, where the code that it contains is used to determine the sequence of amino acids in the protiens which are synthesised there. 

It is the sequence of nucleotides bases on the mRNA that is referred to as the genetic code. 

The mRNA code is derived from DNA but is complementary (not identicle) 

Codon - refers to the sequence of three bases that code for a single amino acid.

Features of the Gentic Code

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

a few amino acids have only a single codon

The code is a degenerate code (most amino acids have more than one codon)

THere are three codon that do not code for any amino acids. These are called STOP codons and mark the end of a polypeptide chain

THe code is non-overlapping, eah base in the sequence is read only once. Thus…