Gregor MendelSpec 3.11B
Gregor Mendel was a monk who worked out the basis of genetics by breeding pea plants in the mid-1800s. He chose characteristics with clear alternatives, such as tall or short plants, and purple or white flowers.
- He crossed plants with different characteristics and counted the characteristics of the offspring over several generations.
- He found that characteristics are passed on as separate inherited factors, one from each parent. We now call these factors genes.
- He showed that some factors are dominant and others are recessive. For example, crossing pure-breeding tall plants with pure-breeding short plants gave all tall plants. Crossing those offspring with each other gave about three tall plants for every one short plant.
Difficulties before the mechanism was discovered
- Nobody knew about genes, DNA or chromosomes, so there was no mechanism to explain how characteristics are passed on.
- The behaviour of chromosomes during cell division and fertilisation had not been seen, so his ideas could not be linked to anything observable.
- His work was not recognised or understood at the time. It was only appreciated after the structures and processes involved in inheritance were discovered.