The Genetic Code

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The Genetic Code

The genetic code is carried by an amazing molecule called Deoxyribonucleic acid, or DNA to its friends. DNA is an amazingly long and complicated molecule.

The DNA is found in the nucleus of all cells. It is formed into X-shaped bundles called chromosomes.

In human cells, except for eggs and sperm, there are 46 chromosomes. These are divided into 23 pairs.

Each chromosome has the appearance of two knitted sausages tied together in the middle.

The more scientific description would be that a chromosome is made up of two chromatids held together in the middle by a centromere. You choose which is easier to remember!

If you start to unpick each of the chromosomes you get down to a single thread which is the DNA.

This DNA strand looks a bit like a ladder twisted into a double helix. The rungs of the ladder are made up of pairs of base molecules connected to each other.

It is the order of the bases (that form the rungs across it like on a ladder) that carry the actual genetic code.

To make things a bit easier for once, there are only 4 different types of bases. Each is usually known by the first letter of its name:

  • Adenine (A),
  • Cytosine (C),
  • Guanine (G),
  • Thymine (T).

Even easier is the fact that the order the bases join up to form the 'rungs' is fixed.

Adenine and Thymine always join together, and Cytosine and Guanine always join.

But so what?

Nice molecule, but what does it actually do?

Each group of 3 bases on one side of the DNA carries the genetic code for one of the 20 different amino acid molecules.

Once the whole code for one gene is read the cell can make the specific protein. Each gene codes for one complete protein. Many of these proteins are actually enzymes.

So the chromosomes in each cell contain every gene needed to create a new human cell or whole body!

Or a plant or animal!


It's like carrying around quite a stack of filing cabinets each stuffed full of sheets with instructions on how to build a new you! And that's in each and every cell.