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LET'S EXPLORE The human body

What are genes?

The DNA molecule under a microscopeThe DNA molecule under a microscopeHow you look, how tall you are, whether your hair is straight or curly—all these and more are decided by your genes. Genes are the set of coded instructions found in every cell in your body. Your genes are unique to you (unless you are an identical twin, in which case you share this code with your twin). They contain all the information your body needs to develop, grow and maintain itself through life.

Chromosomes inside a cell nucleusChromosomes inside a cell nucleus

Diagram of DNADiagram of DNA


Coiled up inside the nucleus of each of your body’s cells are long strands of a substance called DNA. Seen under a powerful microscope, DNA looks like a twisted ladder. The “rungs” of the ladder are made of four different chemical units, linked in pairs. There are millions of rungs. The order of the units down each ladder forms an extremely long and detailed code. This contains the instructions your body needs to grow, develop and work properly. 

These instructions are called genes. They help decide, for example, the colour of your eyes, the shape of your nose and whether you are left-handed or right-handed.

How many genes do you have? The answer is about 23,000. That’s only slightly more than a tiny roundworm has. A mouse has around 30,000. This shows that the size of a living thing is not related to the number of genes it has.

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