DNA and genes
All living things are made of tiny ‘building blocks’ called cells.
Each cell contains inherited genetic information (packaged in the form of genes). A gene is made of a length of DNA (deoxyribonucleic acid) that has a message encoded in its chemical structure. Genes are the instructions that give organisms their particular characteristics - for example, your genes code for your hair colour and eye colour.
Although the chemical building blocks of DNA are the same for every living organism, the ordering or sequence of the chemicals varies and it is this variation that determines an organism’s physical make-up and features. By altering the sequence within DNA, inserting new sequences, or turning off certain genes, an organism’s characteristics can be changed.