註釋
Your genes are an instruction manual for your body. Hidden inside almost every cell in your body is a chemical called DNA. A gene is a short section of DNA.
Your genes contain instructions that tell your cells to make molecules called proteins. Proteins perform various functions in your body to keep you healthy. Each gene carries instructions that determine your features, such as eye colour, hair colour and height. There are different versions of genes for each feature. For example one version (a variant) of a gene for eye colour contains instructions for blue eyes, another type contains instructions for brown eyes.
A double helix
Here you can see the four bases that make up your genes and DNA. The bases are arranged in two long strands that form a spiral called a double helix.
What are Genes made of? Hidden inside almost every cell in your body is a chemical called DNA. A gene is a short section of DNA. DNA is made up of millions of small chemicals called bases. The chemicals come in four types A, C, T and G. A gene is a section of DNA made up of a sequence of As, Cs, Ts and Gs. Your genes are so tiny you have around 20,000 of them inside every cell in your body! Human genes vary in size from a few hundred bases to over a million bases.
Every human has around 20,000 genes and 3,000,000,000 bases. Your entire sequence of genes and bases is called your genome.