Biology

• Continuous variation


  Eg. height, eye colour, shoe size
• Discontinuous variation


  Eg. tongue rolling, ear lobes, blood type
• Variation


  Phenotype = effects of genes + environment
• The nucleus contains chromosomes
• Chromosome


  Contains genes
• Humans contain 46 chromosomes (23 pairs)
• Cell


  Also known as a diploid cell
• Body cells


  Made from a type of cell division known as Mitosis (not in egg or sperm cells)
• Cell division in testes and ovaries


  Known as meiosis
• Sperm and eggs


  Called gametes
• Sex cells have 23 chromosomes
• Zygote


  Has 46 chromosomes
• Females


  Have XX chromosomes (two large)
• Down syndrome has 3 chromosomes in the 21st pair
• Homozygous


  BB or bb
• Gene


  A short section of DNA that codes for a characteristic
• Phenotype


  The outward appearance of an individual