Genetics
Part 1
The Blending Hypothesis
A Trait _______________________________________________________ ___________________
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 In the early 1800’s many biologists believed in the Blending Hypothesis
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 A tall plant and a short plant would produce ____________ ___________________
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 Genetics – ____________________________________________________ ___________________
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The Father of Genetics- Gregor Mendel
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 Gregor Mendel (1822-1884)
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 Austrian Monk
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 Pea Plant Experiments (why? ______________________________ ___________________
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 Mendel studied _____________________________________ or “factors” ___________________
from one generation to the next
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 These factors are now called genes
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Mendel’s Breeding Experiments
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 Mendel bred plants for years to ensure that they were true-breeding
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 True-breeding - _________________________________________
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 Mendel Cross-fertilized ___________________________________ ___________________
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 Mendel expected ___________________________
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 IE: Tall pea x Short pea resulting in Medium height plants
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 In Mendel’s experiments the true-breeding plants were called the _______
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 A hybrid _______________________________________________ ___________________
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Genetics
Part 1
Some Mendelian Conclusions:
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Mendel and Alleles:
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 Mendel and Crosses:
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 Law of segregation
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 _______________________________________________________ ___________________
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 Law of dominance:
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 ______________________________________________________ ___________________
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Punnett Squares
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 Punnett Squares are tools used to determine ________________________ ___________________
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Sample Problem
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Homozygous – ______________________________________
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Let’s say you are Mendel. You take a pure-breeding
pea plant that is tall (TT) and you combine it with a
pure-breeding pea plant that is short (tt). What would
their possible offspring be?
Which of the plants in the sample are homozygous?
Heterozygous – _____________________________________
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Which of the plants in the sample are heterozygous?
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Genetics
Part 1

The offspring would look something like this
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Why are all the offspring tall?
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Dominant – _________________________________
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Recessive – _________________________________
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If an individual is Homozygous Dominant _________
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If an individual is Heterozygous _________________
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Example: TT = tall
Example: Tt = tall
If an individual is Homozygous Recessive _________
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Example: tt = short