The friar who counted peas · Grade 8

The passage and its 6 questions

Directions: Read the passage carefully. Then answer the questions in full sentences.

• In a monastery garden in Brno, in what is now the Czech Republic, a friar named Gregor
• Mendel spent about eight years growing peas. Between 1856 and 1863, he raised many thousands of plants. People had long known that children resemble their parents, but nobody could explain the rules. Many believed that the traits of two parents simply blended together, like mixing paints.
• Mendel chose peas wisely. They grow quickly, produce many seeds, and have traits that come in clear either-or forms: tall or short stems, purple or white flowers, round or wrinkled seeds. He could also control which plants bred with each other by moving pollen by hand. Above all, Mendel did something unusual for a biologist of his time: he counted. He recorded his results as numbers and looked for patterns.
• When he crossed purebred tall plants with purebred short plants, every offspring grew tall. The short trait seemed to vanish. But when those tall offspring pollinated themselves, short plants reappeared in the next generation, about one short plant for every three tall ones. The same three-to-one ratio showed up for flower color, seed shape and the other traits he studied. Blending could not explain this. Instead, Mendel reasoned that each plant carries two "factors" for each trait, one from each parent. One factor can hide the other without destroying it, and the hidden one can return in later generations.
• Today we call Mendel's factors genes, and their versions alleles. Mendel published his work in 1866, but few scientists understood its importance, and he died in 1884 largely unknown as a scientist. In 1900, other botanists rediscovered his paper, and the science of genetics was born. Every Punnett square drawn in a classroom traces back to a patient gardener with a notebook full of numbers.
• 1. Give two reasons pea plants were a good choice for Mendel's experiments.
• 2. What did many people believe about heredity before Mendel, and how did his results challenge it?
• 3. What does the word "purebred" most likely mean in paragraph 3?
• 4. Copy the sentence that explains Mendel's idea of "factors."
• 5. If Mendel grew 400 plants in the second generation, about how many would you expect to be short? Show your reasoning.
• 6. How would the passage change if it were told from another point of view?