New News Biology #57

Gregor Mendel & History of Genetics

Gregor Mendel - founding father of genetics who lived in the mid 1800’s and lived in a monastery. While he was living in his monastery, he discovered that the size and pod color of pea plants were passed down generation by generation.

Mendel’s experiment:

He began by breeding two pea plants - one with green pods and one with yellow pods

He discovered that all the resulting offspring were yellow pea plants (with yellow pods)

Then he bred these yellow pea plants together again, and now he discovered 1 in 4 of the plants had green pods, while the other 3/4 were still yellow.

Mendel reasoned that the reason this could be true was because of what he called “hereditary units”, which came in two kinds, recessive and dominant. The recessive traits (green pods) were only expressed if the plant got “hereditary units” of green from both parents. So all the yellow pea plants of the 2nd generation still had the hereditary units for green pods, but they weren’t being expressed because they were recessive.

Mendel also experimented with the height and flower colors, and he discovered the same pattern. Back in the time that Mendel discovered this, which was in the 1800’s, scientists didn’t know anything about DNA or genes or chromosomes. It was only in the late 1800’s did scientists discover chromosomes and observed how they behaved during cell division. It was only until the early 1900’s did scientists discover the similarities between chromosomes and hereditary units (a.k.a genes). The double helix structure of DNA was discovered in the 1950s. In 2003, the entire sequence of genetic bases that made up human DNA was decoded by scientists.