How does DNA do it?

The main job of DNA is to make the proteins that living things need to grow. So lets look a little closer at proteins.

Proteins are large molecules made of smaller molecules called amino acids. Proteins have special shapes that help them to bind tightly to specific other molecules in the cell.

 

Proteins do not start with this shape. They start as a long chain.

 

DNA is the instructions for building the chain.

 

These are the steps for building a protein.

STEP 1 - Copy the DNA

The DNA stays safely tucked away in the nucleus so we need a working copy of the information. The DNA is unzipped and copied. This is called transcription. (You can remember this by thinking of the trans as in transport and the script as in writing.)

STEP 2 - Take the copy out of the nucleus

The RNA carries a copy of the DNA out of the nucleus and to the ribosomes. The type of RNA that carries the message is called messenger RNA or mRNA for short.

STEP 3 - Translate the message

DNA is a sequence of 4 different bases, A, T, G and C. Messenger RNA substitutes a U for the T when the copy is made, but you still have only 4 possible choices in your code.

A, U, G and C

Proteins are made from 20 main amino acid molecules.

Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, Val

To go from 4 to 20 the mRNA is read in groups of three. This is called translation.