AQA GCSE Biology

Revision Notes

6.3.3 The Understanding of Genetics

Mendel's Work on Genetics

  • Gregor Mendel was an Austrian monk
  • He was trained in mathematics and natural history at the University of Vienna
  • In the mid-19th century, Mendel carried out breeding experiments on plants
  • He studied how characteristics were passed on between generations of plants
  • For example, he conducted studies with pea plants and looked at how the height characteristic was inherited

Mendel pea plant crosses (1), downloadable IGCSE & GCSE Biology revision notes

  • One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
  • Using the example above, Mendel showed that height in pea plants was the result of separately inherited ‘hereditary units’ passed down from each parent plant to the offspring plants – this particular experiment showed that the ‘unit’ for tall plants (T) was dominant over the ‘unit’ for short plants (t)
  • His work eventually provided the foundation for modern genetics
  • The importance of Mendel’s discovery was not recognised until after his death:
    • His studies were totally new to science in the 19th century
    • There was no knowledge of the mechanisms behind his findings (DNA, genes and chromosomes had not been discovered yet)

Chromosome Behaviour

  • In the late 19th century and early 20th century, the behaviour of chromosomes during cell division was observed
  • Scientists realised that chromosomes behaved in a very similar way to Mendel’s ‘hereditary units’
  • Scientists believed Mendel’s ‘units’ must be located on chromosomes
  • We now know that this is true and call these ‘units’ genes

Discovery of DNA Structure

  • In the mid-20th century (1953 to be precise) the structure of DNA was determined and the mechanism of gene function worked out
  • This scientific work by many scientists led to the gene theory being developed

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now