Mendel's Work - Gidemy Class Notes

Gregor Mendel was an Austrian monk
He was studied 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
- In the first experiment, he crossed a tall pea plant with a dwarf pea plant
- In the second experiment, he crossed two of the tall offspring together

The pea plant crosses were originally carried out by Mendel to investigate the inheritance of characteristics

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)
He also carried out experiments to show how other characteristics of pea plants are inherited in the same way
- E.g. Flower colour

Three important conclusions about hereditary in plants were reached
- Characteristics are determined by ‘hereditary units‘ and these hereditary units are passed on from parent to offspring unchanged
- The offspring receives one ‘hereditary unit’ from each parent
- Hereditary units can be dominant or recessive ( a dominant characteristic is always expressed when present)

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)