DNA and genes

• DNA


  Deoxyribonucleic acid, the chemical that all of our genetic material is made of
• DNA


  • It's a polymer made up of lots of similar units stuck together
  • It has two strands which are stuck together to form a double helix
• If you unraveled all the DNA in a single cell, the strand would be over two meters long</b>
• Chromosome


  A really tight coil of DNA, each cell has 46 chromosomes
• There are 23 different types of chromosomes, with two of each type (one from each parent)
• Sex chromosomes


  The 23rd pair, consisting of an X chromosome and a Y chromosome
• Chromosomes only look like an X shape just before cell division
• Gene


  A small section of DNA that codes for a particular type of protein
• There are only 20 different types of amino acids, but they can be combined in many different sequences to form thousands of different proteins
• Genome


  The entire set of genetic material in an organism
• Scientists have now worked out the complete human genome, which allows them to identify genes linked to certain diseases
• Genomes can be used to trace the migrations of our ancestors