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The case: a monastery garden, 1856 to 1863
Gregor Johann Mendel was a monk teaching at Brno in what is now the Czech Republic. Over eight growing seasons he raised roughly twenty-eight thousand garden pea plants, Pisum sativum, and counted their offspring. He presented the work in 1865 and published it in 1866, and almost nobody read it. It was rediscovered independently in 1900 by three botanists — de Vries, Correns and Tschermak — and only then did Mendel become the Father of Genetics.
The choice of plant is itself an exam question. The pea has a short life cycle, produces many seeds, is naturally self-pollinating but can be cross-pollinated by hand, and shows seven traits that come in two clean, non-overlapping forms — tall or dwarf, round or wrinkled, with nothing in between. Blurred traits would have hidden the ratios. Mendel found them because he picked a plant that could not blur.
1. Mendel carried out his classic experiments on heredity using which organism?
2. In a monohybrid cross, the phenotypic ratio obtained in the F2 generation is —
3. The F2 phenotypic ratio of a dihybrid cross is —
4. The sex of a human child is determined by —
5. How many pairs of chromosomes are present in a normal human body cell?
6. Which of the following is an X-linked recessive disorder?
7. The genotypic ratio obtained in the F2 generation of a monohybrid cross is —
8. Down syndrome in humans is caused by —