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Heredity
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
|
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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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