What is DNA?

You've probably heard these sayings:
'a chip off the old block'
'like father, like son'
'she's got her mother's eyes'
'like two peas in a pod'
… they're not meant to be taken literally, but are all commenting on how we inherit different characteristics from our parents - it's all to do with our genes (not jeans!)

DNA (or deoxyribonucleic acid) is the genetic material found in animals and plants which contains all the instructions for their development and day-to-day activity.
Imagine a Russian doll used to demonstrate the different layers and decreasing scales of material within our bodies:

A person is made up of organs, which in turn are made of living cells.

Inside each cell is a nucleus and inside this are 46 chromosomes. Each chromosome contains one long, tightly packed molecule of DNA.

Genes are sections of this molecule, each containing the coded information that makes each individual unique, apart from identical twins.
Variations in the arrangement of this code has been likened to the ways that the 8 musical notes can be sequenced to form all types of music - from Hip-Hop to Bach!.
Our genetic material is microscopic; it's been estimated that if all of our DNA were unraveled, it would reach to the Sun and back 30 times!

The DNA molecule is made of two strands of sugar and phosphate, linked by nucleotide bases, rather like a twisted rope ladder. The 4 bases, or ladder rungs, pair up in a particular way:
Adenine to Thymine
Cytosine to Guanine.
DNA is a special kind of molecule because it can make exact copies of itself by splitting down the 'rungs' and each base re-joining with another pair (A - T and C - G).