Transcript Mendel - My CCSD

10.1 Mendel’s Laws of Heredity
Part 1
Heredity
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Why do we look the way we look?
Heredity
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We are all unique, but we have things in
common with our family members.
Heredity
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Characteristics that are inherited
are called traits.
Bent pinky
Tongue rolling
Detached earlobe
Hitchhiker’s thumb
Widow’s peak
Heredity
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These are traits you got from your parents.
The passing on of characteristics from
parents to offspring is called heredity.
Genetics is the branch
of biology that studies
heredity.
Mendel’s Research
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Austrian Gregor Mendel
wanted to know why offspring
look like their parents.
Mendel began to breed pea
plants to study the inheritance
of their traits.
Mendel’s Research
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Garden pea plants reproduce sexually.
Plants make two different sex cells,
male and female
Sex cells are called
gametes.
Mendel’s Research
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A pea plant makes both male and female
gametes.
Male pollen
Female ovule
located in pistil
Mendel’s Research
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Pollination is the transfer of male pollen
grains to the pistil.
Mendel’s Research
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Fertilization happens
when the male and
female gametes meet
and develop into a
seed.
Mendel’s Research
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Mendel could let a plant pollinate itself
or he could take pollen from one and
place on pistil of another
Mendel’s Research
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Mendel studied one trait at a time
Monohybrid crosses – study breeding of
plants that are the same except for one trait
A hybrid is the offspring of parents that have
different forms of a trait, tall or short height
Mendel’s Research
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Mendel started with two plants,
one tall and one short.
He cross-pollinated them and planted the
seeds that formed.
Mendel’s Research
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The first generation of
offspring were all tall.
Mendel’s Research
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He let those plants self
pollinate and planted
the seeds again.
The second generation
of offspring were
mostly tall, but there
were a few short ones.
3 tall : 1 short
Mendel’s Research
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Mendel found seven different traits that
showed the same pattern,
3:1 in the second offspring generation
Mendel’s Research
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Mendel concluded that each plant has two
factors that control each trait, one from each
parent.
He did not know what these factors were,
we now call them alleles.
Alleles are alternative forms of a gene that
determine the visible trait.
Mendel’s Research
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So, why did the first
offspring generation
(F1) have all tall plants?
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Why did the second
offspring generation
have 3 tall: 1 short
plant?
Mendel’s Research
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So, why did the first offspring generation (F1)
have all tall plants?
Mendel called the form that showed
dominant
The trait that disappeared he called
recessive
Mendel’s Research
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Why did the second offspring generation
have 3 tall: 1 short plant?
The plants in F1 had
one allele for tall and
one for short.
Since tall is dominant
all were tall.
Mendel’s Research
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When F1 pollinated and produced seeds,
some of the next generation (F2) had two
short alleles.
F2 generation had
3 tall plants for
every 1 short plant