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How do we find out how bodily traits are inherited?

Read the Story Time about Gregor Mendel. This monk, who liked to putter around in the monastery garden, made a most profound discovery.  Between 1856 and 1863 he cultivated and tested at least 28,000 pea plants, carefully analyzing seven pairs of seed and plant characteristics (see table below). He saw that many of these traits are inherited in a very clear and simple way. 

However, what seems simple today was not so simple for Mendel, because he had no prior information about how things worked. He had only his observations of what happened in the offspring when he bred one kind of plant (he worked with peas) with another kind of plant.

The seven pairs of traits that Mendel studied in the peas were: 
Trait: Most peas: Some peas:

1. Surface of ripe seed Smooth Wrinkled
2. Color of seed albumen Yellow Green
3. Color of seed coat Grey White
4. Form of ripe pods Inflated Constricted
5. Color of unripe pods Green Yellow
6. Position of flowers Axial Terminal
7. Length of stem  Tall Dwarf

Remember that Mendel worked almost 150 years ago when nobody knew about genes or even the structures (chromosomes) that carry genes. Mendel and his neighbors did know about the role of heredity in farming. If a farmer breeds all his cows to a large, beautiful bull, most of the offspring will be larger and more beautiful than if a scruffy bull had been used. 

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