DNA & the Genome (AQA GCSE Biology): Revision Note

The genome

• The entire set of the genetic material of an organism is known as its genome

• Biologists now know the entire human genome (they have worked out all the genes that are found in humans)

The structure of DNA

• The genetic material in the nucleus of a cell is composed of a chemical called DNA

• DNA, or deoxyribonucleic acid, is the molecule that contains the instructions for growth and development of all organisms

• DNA is a polymer made up of two strands forming a double helix

• DNA is contained in structures called chromosomes

• Chromosomes are located in the nucleus of cells

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Genes

• A gene is a short length of DNA found on a chromosome

• Each gene codes for a particular sequence of amino acids

• These sequences of amino acids form different types of proteins

• There are many different types of proteins but examples include:

  • structural proteins

  • enzymes

  • hormones

• Genes control our characteristics as they code for proteins that play important roles in what our cells do

The Human Genome Project

• The Human Genome Project (completed in 2003) was the name of the international, collaborative research effort to determine the DNA sequence of the entire human genome and record every gene in human beings

• This was an important breakthrough for several reasons:

  • It has improved our understanding of the genes linked with some diseases and inherited genetic disorders, as well as helped us to find treatments

  • It has facilitated the study of past human migration patterns, as populations of humans living in different parts of the world have developed small differences in their genomes