Transcript 11-1 The Work of Gregory Mendel

11-1
The Work of
Gregory
Mendel
Flora
I
Genetics
 Genetics
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– the study of heredity
Essential to understanding biology
Mendel
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Mendel knew the following:
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Each part of each flower produces pollen
(anther)
Other portions produce female reproduction
cells
The two join and fertilization occurs
Gametes – sex cell
Fertilization – male and female reproduction
cells join to form a new cell
True-breeding – if allowed to self-pollinate, they
would produce offspring identical to
themselves
Genes and Dominance
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Mendel studied plant traits
Trait – specific characteristic of an organism
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Ex: seed color, plant height, etc.
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Mendel studied 7 traits:
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Seed shape
Seed color
Seed coat
Pod shape
Pod color
Flower position
Plant height
Cont.
 Mendel
crossed plants with these seven
contrasting traits and studied their
offspring
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Parents – called “P” generation
Offspring – called “F1” generation
A cross between parents with different traits
are known as hybrids
Mendel’s Two Conclusions
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Biological inheritance is determined by
factors that are passed on from one
generation to the next
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These traits are called genes
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Genes – sequence of DNA that codes for
a specific protein thus determining the trait
Some genes have contrasting forms
called alleles
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Alleles – one of a number of different forms
of a gene
Cont. Mendel’s Two
Conclusions
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The principal of dominance states that
some alleles are dominant and others
are recessive
An organism with a dominant allele for a
specific trait will always exhibit that form
of that trait.
Recessive alleles will only exhibit that trait
when the dominant allele is absent
Ex: Mendel’s Experiment
Segregation
 Did
the alleles present in the P generation
disappear from the F1 generation?
 Mendel allowed 7 kinds of F1 hybrid plants
to self-pollinate producing an F2
generation
 See page 265
Law of Segregation
 when
any individual produces gametes,
the copies of a gene separate, so that
each gamete receives only one copy. A
gamete will receive one allele or the
other
 Each F1 plant produces two types of
gametes
 Ex: Tt x Tt