Dear Aarsha mv,
I assume you want to get the codons from your piece of DNA, but correct me if I am wrong.
Let us take the example of a piece of DNA coding for the protein insulin (I took a part of this piece of DNA).
Define a string of nucleotides as being your DNA sequence:
your_DNA = 'CTCGAGGGGCCTAGACATTGCCCTCCAGAGAGAGCACCCAACACCCTCCAGGCTTGACCGGCCAGGGTG';
To get the codons you can use 'reshape', as was suggested by Stephen Cobeldick and John D'Errico.
Use reshape as follows:
codons = reshape(your_DNA(:),3,length(your_DNA)/3)'
In a 'real life' scenario you would probably need a workaround if length(your_DNA) is not a number that can be divided by 3.