genetic variation

• a mutation is a rare random change in n organisms DNA that can be inherited
• some variants can have a small influence on the phenotype. e.g eye colour is controlled by more than one gene. a mutation can change the eye colour a bit. (no big difference)
• Most mutations have no affect on an organism's phenotype
• Most genetic variants have little or no effect on the protein that the gene codes for
• Genetic variant

  A different form of gene
• Mutations

  The sequence of DNA bases in the gene is changed
• The sequence of DNA bases in the gene is changed

  Produces a genetic variant
• Mutations


  Lead to changes in the protein that it codes for
• Gene


  The sequence of DNA bases in a gene codes for the amino acids that make up a protein
• Very occasionally variants can have such a dramatic effect that they determine the phenotype
• Cystic fibrosis

  A genetic disorder that can be caused by the deletion of just three bases
• The gene


  Codes for a protein that controls the movement of salt and water into and out of cells
• Mutated gene


  The protein produced by the mutated gene doesn't work properly
• proteins produced by the mutated gene doesn't work properly so: This leads to excess mucus production in the lungs and digestive system
• Excess mucus production in the lungs and digestive system

  Can make it difficult to breathe and to digest food
• Variants


  Can affect coding and non-coding DNA
• DNA


  Molecule that contains a lot of genes (sequences of DNA bases) that code for particular proteins and a lot of sequences of bases that don't code for proteins (non-coding DNA)
• Mutations

  • Coding DNA
  • Non-coding DNA
• Mutations in coding DNA

  Affect the proteins coded for by the amino acid
• Mutations in coding DNA

  Can affect the proteins structure and the way that it functions
• Mutations in non-coding DNA

  Can affect how genes are expressed
• Mutations in non-coding DNA

  Can stop the transcription of mRNA so the protein coded for by that gene is not produced at all