Genetics

• Meiosis creates four genetically different daughter cells, that are haploid. There are two divisions that take place in order to produce the gametes.
• DNA is found in the chromosone of a nucleus. It has a double helix structure containing four bases ( adenine, thymine, cytosine & guanine) and a sugar-phosphate backbone.
• The bases are complimentary and are bonded by hydrogen bonds. The order of these bases in a gene codes for a protein.
• An allelle is a different version of a gene. Allelles express different characteristics based on whether it is homozygous, heterozygous or dominant, recessive.
• Sex chromosones determine what sex you are: XY (male) and XX (female).
• Gene mutation is a change in the DNA sequence of a gene. It can cause genetic variation, but that can also be caused by environmental factors.
• DNA extraction: core practical

  • homogonise cells by mashing up fruit, add soap (breaks down nuclear/ cell membrane), add salt and juice (protease).
  • filter to remove insoluble material, add ice-cold ethanol (precipates DNA).