The life of Gregor Mendel 1822 1884 Born

The life of Gregor Mendel 1822 – 1884 Born into a German family in, what is now, the Czech Rupublic but what was then called the Austrian Empire. He wasn’t given the name “Gregor” by his parents but instead was given it when he joined the Augustinian Friars. He became a Friar because it allowed him to have a free education.

1822 A Timeline of Mendel’s Life • Mendel was born on the 22 nd of July 1822 in the Austrian Empire (now Czech Republic); • In 1843 Mendel joined the Augustinian Monastery in Brno in order to pursue his studies without worrying how to pay for them; • Four years later on the in 1847 Mendel was ordained as a priest; • In 1851 Mendel was sent to the University of Vienna to study Botany, Zoology, Chemistry and Physics; • In 1854 Mendel returned to the Monastery to teach Natural Studies at Brno Technical School; • In Mendel’s free time at the school he was able to conduct his most famous experiements. These took place between 1854 and 1868; • In 1864 Mendel obtained results that lead to the famous Law of Segregation; • In 1865 Mendel presented his experimental findings to Brno Society for the Study of Natural Science; • In 1866 Mendel’s findings with plants were published; • Mendel died in 1884

Mendel’s Experimental Work • When Mendel taught at Brno Technical School he studied thousands of plants, but mainly pea plants because they had distinctive characteristics and were quick to grow. • Mendel created hybrids of the pea plants by acting as the pollinator and carefully controlled which two plants created a new generation. • Mendel worked with thousands of plants to observe their seven different traits: 1. 2. 3. 4. 5. 6. 7. Flower Colour (purple or white); Flower Position (axial or terminal); Stem length (short or tall); Seed Shapes (round or wrinkled); Seed Colour (yellow or green); Pod Shape (inflated or constricted); Pod colour (yellow or green). • Mendel cross-pollinated different kinds of pea plants in order to observe their characteristics. He recorded any findings of new generations and then repeated this process by pollinating the new generation plants that he created.

Mendel’s Experimental Work • An illustration of the different traits that Mendel measured during his pea plant experiments:

Mendel’s Findings • At first Mendel cross-pollinated smooth yellow pea plants with wrinkly green peas. He found that every pea in the first generation crop (f 1) was yellow and round. Therefore, yellow dominated green and round dominated wrinkly. Therefore Mendel learned that there are 2 kinds of traits – dominant and recessive. He also learned that the inheritance of traits from parents is determined by genes. • Mendell then planted seeds from the all-yellow and all-round crop, f 1, and selfpollinated them after they grew-up. Most of this f 2 generation were yellow and round but SOME were green and wrinkly. Mendel repeated this result several times and the f 2 generation always had a 3: 1 ratio of yellow: green and round: wrinkly peas. • In the pollination process each offspring inherits one gene from each parent. So the possible combinations of colour can be: YY, Yg, g. Y or gg. Three of these combinations give a yellow plant and only one gives a green plant. This is beacuse a dominant trait needs only one gene (or allele) to prevail, but a recessive trait needs two. This is why the ratio of occurences between dominant traits and recessive traits is 3: 1.

Mendel’s Findings • The following are the important outcomes of Mendel’s experiments: 1. The inheritance of each trait is determined by genes that are passed on to descendants unchanged; 2. A descendant inherits one gene for each trait from each parent; 3. A trait may not show up in an individual but can still be passed on to the next generation. 4. Principle of Segregation: each parent has two alleles for any given trait, yet only passes on one of these alleles to their offspring. Which allele is inherited is a matter of chance and happens during the process of sex cell formation. 5. Principle of Independent Assortment: The Law of Independent Assortment states that separate genes for separate traits are passed independently of one another from parents to offspring. That is, the biological selection of a particular gene in the gene pair for one trait to be passed to the offspring has nothing to do with the selection of the gene for any other trait. More precisely, the law states that alleles of different genes assort independently of one another during gamete formation. 6. Principle of Dominance: Recessive alleles will always be masked by dominant alleles.

Controversy The results of Mendel’s experiments were the subject of considerable dispute because: • When Mendel was alive many scientists believed that parents passed traits to their offspring through blended inheritance. Blended inheritance states that the traits from each parent are averaged together. Mendel’s work was not rediscovered until the 20 th century when people started to realise it’s importance. • Mendel also received a lot of criticism from a scientist named Fisher who doubted the execution of Mendel’s experiments. Fisher was also suspicious that Mendel discovered the exact ratio of 3: 1, he suspected that the actual results may have been biased since they were surprisingly close to the expected results.