DNA & the Genome (AQA GCSE Biology: Combined Science)

• 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 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

Genes are short lengths of DNA that code for a protein. They are found on chromosomes

• 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 some example of these could be:
  • structural proteins such as collagen found in skin cells
  • enzymes
  • hormones

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

• 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 a very important breakthrough for several reasons:
  • From a medical perspective, as it has already and will continue to improve our understanding of the genes linked with different types of disease and inherited genetic disorders, as well as the help us in finding treatments
  • The human genome has also made it possible to study human migration patterns from the past, as different populations of humans living in different parts of the world have developed very small differences in their genomes!