What is a genome?

A genome is an organism’s complete set of genetic instructions. Each genome contains all of the information needed to build that organism and allow it to grow and develop. 

Our bodies are made up of millions of cells (100,000,000,000,000), each with their own complete set of instructions for making us, like a recipe book for the body. This set of instructions is known as our genome and is made up of DNA. Each cell in the body, for example, a skin cell or a liver cell, contains this same set of instructions:

  • The instructions in our genome are made up of DNA.
  • Within DNA is a unique chemical code that guides our growth, development and health.
  • This code is determined by the order of the four nucleotide bases that make up DNA, adenine, cytosine, guanine and thymine, A, C, G and T for short.
  • DNA has a twisted structure in the shape of a double helix.
  • Single strands of DNA are coiled up into structures called chromosomes.
  • Your chromosomes are located in the nucleus within each cell.
  • Within our chromosomes, sections of DNA are "read" together to form genes.
  • Genes control different characteristics such as eye colour and height.
  • All living things have a unique genome.
  • The human genome is made of 3.2 billion bases of DNA but other organisms have different genome sizes.

If printed out the 3.2 billion letters in your genome would:

  • Fill a stack of paperback books 200 feet (61 m) high
  • Fill 200 500-page telephone directories
  • Take a century to recite, if we recited at one letter per second for 24 hours a day
  • Extend 3,000 km (1,864 miles), that's about the distance from London to the Canary Islands, Washington to Guatemala or from New Delhi to Hanoi. 
If printed out 1 mm apart, the DNA letters in your genome would extend 3,000 km.

If printed out 1 mm apart, the DNA letters in your genome would extend 3,000 km.


This page was last updated on 2017-01-06