Work of Mendel

• Describe his experiment 


  • Crossed 2 pea plants of different heights (a tall x dwarf one)
  • Then bred the offspring together
  • Found that 3 tall offspring were produced for every 1 dwarf
• What were Mendel's conclusions

  • Characteristics in plants determined by 'hereditary units'
  • Hereditary units passed onto offspring unchanged from both parents
  • Hereditary units can be dominant or recessive
• Why was his work unaccepted

  • He didn't communicate it well so they didnt understand it
  • Published in a scientific journal that wasn't well known
  • Couldn't explain the science behind why characteristics were inherited
• Why did the development of the microscope play an important role

  • Showed what chromosomes looked like
  • Behaviour of chromosomes during cell division
  • Gene function
  • DNA structure also determined
• What is continuous variation

  • Data can be any value in a range
  • Caused by genetics + environment like height
• What is discontinuous variation

  • Data can only take a limited set of values
  • Caused by genetics only like eye colour
• What graph is used during continuous variation

  Histograms
• what graph is used during discontinuous variation

  Bar chart
• How do most mutations affect things

  Have no effect on an organism's characteristics -> neutral mutations
• How do some mutations affect things

  Have a small effect in changing characteristics slightly like hamster having long hair than short hair
• How do mutations affect things rarely

  genetic disorder -> anaemia + Down syndrome