Topic 3

• Complementary base pairs

  Joined together by weak hydrogen bonds
• DNA bases

  • A (adenine)
  • C (cytosine)
  • T (thymine)
  • G (guanine)
• Complementary base pairs

  1. A-T and C-G
• DNA


  Contains coded information that determines inherited characteristics
• DNA structure


  2 strands coiled together to make a double stranded helix
• Nucleotides


  Smaller sub-units that DNA is made up of
• Nucleotide

  Made up of a phosphate group, a sugar, and one of the 4 bases
• Extracting DNA from Fruit

  1. Grind up/crush the kiwi fruit

  2. Add detergent to break up cell wall and membrane

  3. Add salt to make DNA stick together

  4. Filter the mixture to remove insoluble materials

  5. Add ice cold ethanol (alcohol) slowly to precipitate out the DNA

  6. Use a hook/glass rod to remove the DNA
• Chromosome


  Molecule of DNA
• Gene

  Section of DNA coding for a protein (causing a feature)
• Genome

  All of the DNA of an organism
• Phenotype


  Physical appearance
• Genotype


  Genes you inherit
• Gametes

  Sex cells (egg and sperm cells)
• Allele


  A form of a gene
• Dominant allele


  Only need to inherit 1 allele to show the characteristic
• Recessive allele


  Need to inherit 2 alleles to show the characteristic
• Heterozygous


  2 alleles for a gene which are different
• Homozygous


  2 alleles for a gene which are the same
• Homozygous dominant


  2 dominant alleles
• Homozygous recessive


  2 recessive alleles
• Zygote

  Fertilised egg cell (diploid)
• Sex determination


  23rd pair of chromosomes determine gender (sex) and are called the sex chromosomes
• XY

  Causes male characteristics
• XX


  Causes female characteristics