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Photo courtesy of National
Library of Medicine |
In 1857, Austrian
monk Gregor Mendel decided to breed pea plants
in the large monastery garden of Brunn. He loved
botany (studying plants) and he had very much
wanted to become a high school teacher. Unfortunately,
he had failed the teaching exam three times,
so he had to be content with living as a monk.
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Mendel noticed that all of his pea plants had
different characteristics: some had green seeds,
others had yellow; some had tall stems, and others
had short, and so on. He was curious why this was
true, especially when he noticed that sometimes
the offspring portrayed characteristics of the parent(s)
and sometimes they did not. He decided to experiment
with the pea plants (which are excellent for such
experiments because they can self replicate) to
discover why.
The first trait Mendel tested was height. When
he took several short plants and self pollinated
them, they produced seeds that all grew to be short,
just like the parents - that is, they all bred true.
Then, he self pollinated several tall plants and
the resulting seeds (called the F1 generation) all
grew to be tall, meaning they also bred true. The
results of this experiment seem obvious and logical,
that short parents have short offspring and tall
parents have tall offspring; hence, Mendel wasn't
surprised at all by his findings. He was surprised,
however, when he bred a new batch of tall plants
with short plants and found that all the offspring
were tall. Not a single seed of this F1 generation
grew to be short. At first, Mendel believed that
the shortness characteristic had disappeared, but
when he self pollinated the F1 offspring, the second
generation (called the F2 generation) had a mix
of both tall and short plants. Apparently, the shortness
hadn't just disappeared after all!
After conducting more experiments and breeding
more plants, Mendel figured out that in the F2 generation,
there were three tall plants for every short one
(a 3:1 ratio). From this, he concluded that traits,
or characteristics, come in pairs - one from each
parent - and that one trait will have dominance
over the other (tall is dominant over short, for
example). The idea was simple, but very ingenious
for its time.
Mendel studied other traits besides height, including
the color of the seeds and seed coats, the position
of the flowers on the stems, and the shape and color
of the pea pods. It took him eight years and 30,000
pea plants to discover these natural laws of heredity
(now known as the Mendelian Laws). Afterwards, Mendel
wished to publish his findings, but feared that
no one would listen to him because he was only a
monk and not even qualified to teach high school!
Nevertheless, he sent his reports to the most famous
botanist in Europe, Karl Wilhelm von Nageli of Switzerland,
hoping to gain his sponsorship (support of his work).
von Nageli ignored Mendel's work, though, and sent
it back to him. Mendel was able to get his paper
published in a scientific journal several years
later, but - just as he had feared - no one acknowledged
it because he was an unsponsored amateur. Saddened,
he gave up botany and devoted his days to monastic
life. Mendel died in 1884. It was nearly forty years
later when his writings and research were rediscovered
and found to be true.
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