Download Genetics - STEMPREP 2013

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Lecturer: David
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* Mendel conducted an
experiment by crossing
pea plants with green
and yellow peas.
* Dominant allele
*Y
* Recessive allele
*y
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* Heterozygote – a person with 2 different alleles
* For the peas:
* Yy = Yellow peas
* Homozygote – a person with 2 identical alleles
* For the peas:
* YY = Yellow peas
* yy = Green peas
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* The genetic makeup of a
person; whether they are
homozygote or heterozygote
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* Physical characteristics of
an individual’s genotype
* Which is the recessive
allele?
* Which is the dominant
allele?
* Which ones are
homozygous?
* Which ones are
heterozygous?
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* Co-dominance occurs when BOTH alleles are
expressed. There is a mixture of phenotypes or
both phenotypes are expressed.
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* What is this an
example of?
* Why?
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* The generation you begin with to determine
the genotype of subsequent generations is the
parental generation
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* Any following generations are called filial
* F1, F2, F3
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* You decide to cross a purple flower (Pp) and
and a yellow flower (pp). What are the
genotypic ratios for the F1 generation? What
about the phenotypic ratios? (P is dominant
allele, p is recessive allele)
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* Genotype: 1Pp:1pp
* Phenotype: 1:1 (purple:yellow)
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* You decide to cross a heterozygote green pea
(Gg) and a heterozygote green pea (Gg). What
are the genotypic and phenotypic ratios of the
F1 generation? (G – allele for green, g – allele
for brown)
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* Genotype: 1GG:2Gg:1gg
* Phenotype 3:1 (green:brown)
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* You decide to cross a green eyed frog (GG) with
a blue eyed frog (gg). What would the
phenotypic and genotypic ratios be for the F1
generation? (G – dominant allele, g – recessive
allele)
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* Genotype: 100% Gg
* Phenotype: 100% green eyed frogs
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* You decide to cross a frog from the F1
generation of the previous question with a
green eyed frog from the P generation. What
do you expect your genotypic and phenotypic
ratios to be?
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* Genotype: 1GG:1Gg
* Phenotype: 100% green eyed frogs
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* You now decide to cross two F1 generations.
What phenotypic and genotypic ratios do you
expect for the F2 generation?
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* Genotype: 1GG:2Gg:1gg
* Phenotype: 3:1 (green eyed:blue eyed)
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* You performed a cross between 2 flower
plants. 100% of your flowers are red. What are
the possible genotypes for the parental
generation? (R – dominant allele, r – recessive
allele)
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* The parental cross was either:
* RR x rr
* Rr x RR
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* What percentage of heterozygotes would you
expect from a cross between 2 blue birds? (The
allele for blue is recessive)
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* No heterozygotes expected
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* What percentage of heterozygotes and
homozygotes would you expect from a cross
between 2 red birds (Rr)?
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* 50% homozygotes
* 50% heterozygotes
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* A heterozygous bean plant was crossed with a
homozygous bean plant. What percentage of
homozygotes and heterozygotes would you
expect? (R – dominant allele, r – recessive
allele)
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* 50% heterozygotes
* 50% homozygotes
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* Monohybrid vs. dihybrid crosses
* Monohybrid cross – cross of individuals that
contrast by 1 trait
* Dihybrid cross – cross of individuals with 2
different traits
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* Today you will be conducting a genetics lab
with corn
* For the first exercise you will be studying the
cross between parental and F1 corn.
* For the second exercise you will be studying
the the F2 generation
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