We share a lot of DNA with other animals, plants and microorganisms. The table
below shows some figures on shared sequence between species.


 How many genes do we share with them?







Fruit fly


Weed (thale cress)


Bacteria (E coli)


The structure of DNA was discovered in 1953.

We have 30,000- 40,000 genes, each with coding for important functions.

These letters are scrambled several million times to make the genetic code.

The Human Genome Project has a complete catalogue of the Human Genome.

This catalogue will be the size several hundred
average-sized telephone books and

will have the letters A, T, G, C in various permutations and combinations.

We still don't know the function of more than 80 per cent of our DNA.

DNA is found inside every cell in our body (apart from red blood cells).

Each cell contains roughly 2 metres of DNA.

Humans have roughly 100,000,000,000,000 (100 trillion cells).

If you unravelled all of your DNA from all of your cells and laid out the DNA end to end, the strand would stretch
from the Earth to the Sun hundreds of times  (the sun is approximately 98 million miles away from Earth and
6000 times the distance between earth and moon.).

You could fit 25,000 strands of DNA side by side in the width of a single adult hair.

The DNA is tightly coiled up and structured into 46 chromosomes.

Our chromosomes are arranged in pairs. We inherit one copy of the pair from our
mother  and one from our father.

When chromosomes are stained they can be quite easily recognised by their
distinctive stripy patterns. This is used to check whether people have the right
number of chromosomes and check for any rearrangements.

There are approximately 3 billion (3,000,000,000) chemical letters (otherwise
known as bases) in the DNA code in every cell in your body.

This is a massive amount of information. It would fill 200 yellow pages in small type font.

If you tried typing the whole genetic code out (typing at 200 letters per minute) it
would take 29 years (without taking any breaks!).
The DNA is made up of 4 building blocks (an alphabet of 4 letters spelling out the
instructions to help us grow, develop and function).

 The four letters in the DNA alphabet - A, C, G and T - (A = Adenine, T = Thymine, G = Guanine C = Cytosine)
 are used to carry the instructions for making all organisms.

 The sequence of these letters holds the code - just like the order of letters that makes words mean something.
  Each set of three letters corresponds to a single amino acid.

 Sections of DNA that code for proteins are called genes. The complete set of
 genetic information for an organism is called the genome. The latest estimate is
 that there are between 20,000 and 25,000 genes in the human genome.