I' Gregor Mendel father of genetics

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I. Gregor Mendel father of genetics
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a. Inheritance Theory Prior to Mendel

• 1. Traits blended
• Trait characteristics to be passed from parent
  to offspring
• bloodlines thought traits passed through the
  blood
• 2. Problem with blending cannot account for
  unexpected traits

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II. Mendel- the story

• Personal history
• 1. Austrian monk
• 2. Teacher of high school natural science- love
  of evolution, nature, meteorology
• 3. for the fun of it crossed peas and mice-
  saw inheritance patterns
• 4. pea plants- a formal test

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• 5. lets add math
• - importance of statistics and ratios basis
  for his hypotheses
• - problem the math created not used in
  biology previously
• b. The research
• 1. pea plants- why?
• - structure (male and female parts on same
  plant)
• - distinctive traits
• - rapid reproduction
• - ability to control pollination and
  fertilzation

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Steps of Mendel's Experiment
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1.   Mendel studied the inheritance of one trait
(for example plant's height, color of  flowers
or color and shape of seeds).
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2.    Mendel first cross pollinated tall pea
plants (identified as TT, height of plants
in this variety were about six feet
tall) with each other.
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Mendel noticed, that only tall plants were
produced. He came to a conclusion, that the
tall variety of a pea plant, must contain some
factor for tallness.
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3.   Mendel then cross pollinated short pea
plants (identified as tt, height of plants in
this variety were about one foot tall) with
each other.
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X
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In every generation of this plant only short
plants were produced. Once again he concluded
that pea plant must contain some factor for
height (in that variety - for shortness).
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4.   The next step of Mendel's experiment was to
crossed tall pea plants (TT) with short pea
plants (tt). The resulting plants were labeled
Tt and only tall plants were produced.
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All plants were tall
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Labeling

• The standard way of labeling the variation
  information of a trait in a particular organism
  is using two letters. Capital letters represent
  information which is dominant. Lowercase letters
  represent the recessive. The letter being used
  describes a variation (usually the recessive) of
  the trait.
• TT stands for a plant where both pieces of height
  information are dominant - tall. The plant is
  tall.Tt stands for a plant where one piece of
  height information is dominant - tall, and the
  other is recessive - short. The plant is
  tall.Tt stands for a plant where one piece of
  height information is recessive - short, and the
  other is dominant - tall. The plant is tall.tt
  stands for a plant where both pieces of height
  information are recessive - short. The plant is
  short.

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Here we crossed two peas which contained both
tall and short information.
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A cross in which only one trait is studied is
called monohybrid cross .
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5.  Mendel named every generation Starting
generation P (parent) generation. The
following offspring generation was called
F1 - first generation (daughter generation),
F2 - second filial generation, and so on.
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P
F1
F2
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• 2. results from experiments
• - tall x short ----- gt all tall
• - dominant ---- gt tall
• - recessive ---- gt short
• - hybrid x hybrid ---- gt result of crossing F1
  generation- led to the idea of gene forms
• 3. the gene
• - sections of chromosomes coding for a trait
• - alleles forms of a gene (ex tall and short
  for the gene for height)

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• 4. no blending Mendel found that blending was
  not occurring since all traits expressed were
  either dominant or recessive, but not in between
  (ex either tall or short not medium)
• 5. example crosses
• AA x AA aa x aa
• Aa x Aa

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• c. Research rejected
• 1. why?
• - math not previously used in science
• - public skeptical
• - information not understood
• - public distracted by Charles Darwins study on
  evolution
• d. Importance of research
• - evolution provided genetic support for this
  theory
• - modern genetics studies we still use much of
  Mendels conclusions in our own theories/ studies
  in genetics