Unit3 genetics

• The environment

  Factors like Climate, diet, pollution, drugs and ifestyle
• Continuous variation

  When there is a gradual change in a feature and there are no clearly distinct groups eg height. Data would be displayed in a histogram
• Discontinuous variation


  When individuals can be placed into distinct groups or categories eg. blood group. Data would be displayed in a bar chart
• Genome

  An organism's entire genetic material
• Chromosome

  Tiny, thread-like structures made from DNA, which are found in the nucleus of each cell
• Double helix

  Used to describe the structure of DNA
• Gene

  A short section of DNA along a chromosome, that codes for a particular characteristic or protein
• Allele

  Different forms of a gene
• Females

  Have 2 X chromosomes
• Males

  Have an X and a Y chromosome
• What two forms of Cell division

  Mitosis and meiosis
• Mitosis


  Cells produced are all genetically identical to the parent cell
• Meiosis


  Cells produced are all genetically different
• Recessive allele


  Designated by a dominant allele
• Dominant allele


  Overrides a recessive allele
• Genotype


  The genetic makeup eg. BB or Bb
• Phenotype


  The physical characteristics (i.e. what you see) eg. brown or blue eyes
• Homozygous genotype

  Both the alleles are the same eg. BB or bb
• Heterozygous genotype


  The 2 alleles are different eg. Bb
• Diagrams used to work out the results of genetic crosses

  • Genetic diagrams
  • Punnett squares
• Mutation


  A sudden change in a gene or chromosome
• Down's Syndrome is caused by one extra chromosome, making 47 instead of the normal 46
• Cystic fibrosis


  Both parents must be carriers i.e, carry a recessive faulty allele
• What form of call division evolves sperm cells and ova

  Meiosis
• Variation


  The presence of different characteristics between organisms of the same species
• Causes of variation

  • Genes
  • Environment
• Environmental factors

  • Climate
  • Diet
  • Pollution
  • Drugs
  • Lifestyle