DNA

• DNA strands are polymers made up of lots of repeating units called nucleotides. Each nucleotide consists of a sugar, a phosphate group and one 'base'. The sugar and phosphate groups in the nucleotides form a 'backbone' to the DNA strands. The sugar and phosphate groups alternate. 1 of 4 different bases joins to each sugar. The bases are A(adenine), T(thymine), C(cytosine) and G(guanine). A DNA molecules has 2 strands coiled together in the shape of a double helix. Each base links to a base on the opposite strand in the helix. A always pairs up with T, and C always pairs up with G.(TBC)
• (PCC) This is called complementary base pairing. The complementary base pairs are joined together by weak hydrogen bonds.
• Chromosomes are long, coiled up molecules of DNA. They're found in the nucleus of eukaryotic cells. A gene is a section of DNA on a chromosomes that codes for a particular protein. All of an organism's DNA makes up its genome.
• You need to know how to extract DNA from fruit cells: Mash some strawberries and then put them in a beaker containing a solution of detergent and salt. Mix well. The detergent will break down the cell membranes to release the DNA. The salts will make the DNA stick together. Filter the mixture to get the froth and big, insoluble bits of cell out. Gently add some ice-cold alcohol to the filtered mixture. The DNA will start to come out of solution as it's not soluble in cold alcohol. It will appear as a stringy white precipitate that can be carefully fished out with a glass rod.
• What is DNA?

  Polymer made up of repeating units called nucleotides