extremely low

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Asexual Reproduction
Sexual Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
Crossing-over and independent assortment generate
genetic diversity during sexual reproduction.
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Why does sexual reproduction exist?

• Cons
• Need two individuals
• Hard to find mate
• Diseases/Competition

• Pros
• Genetic diversity
• or
• Replace damage DNA

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CB 29.8 and .12
Haploid dominant (algae)
Diploid dominant (fern)
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Why does sexual reproduction exist?

• Cons
• Need two individuals
• Hard to find mate
• Diseases/Competition

• Pros
• Genetic diversity
• or
• Replace damage DNA

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Does a stressful environment lead to sexual
reproduction?
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Asexual Reproduction
Sexual Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
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CB 26.20
Environmental changes occur slowly
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Asexual Reproduction
Sexual Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
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CB 13.5
Producing gametes
Sexual reproduction creates genetic diversity by
combining DNA from 2 individuals, but also by
creating genetically unique gametes.
Producing more cells
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Each pair of chromosomes is comprised of a
paternal and maternal chromosome
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haploid
X 23 in humans
X 23 in humans
diploid
X 23 in humans
Inheritance The interaction between genes
inherited from Mom and Dad.
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Do parents genes/traits blend together in
offspring?
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CB 14.3
In many instances there is a unique pattern of
inheritance. Traits disappear and reappear in
new ratios.
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Genotype
Phenotype
CB 14.6
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Human blood types
CB tbl 14.2
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CB tbl 14.2
One gene with three alleles controls
carbohydrates that are found on Red Blood Cell
membranes
A
A
B
RBC
A
RBC
B
RBC
B
A
B
A
B
A
A
B
B
A
A
B
B
Allele O no carbs
Allele A A carbs
Allele B B carbs
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Human blood types
CB tbl 14.2
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CB tbl 14.2
We each have two versions of each gene
A
A
RBC
A
A
A
So
A
A
A
A
Genotype could be A and A OR A and O
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CB tbl 14.2
Recessive alleles do not show their phenotype
when a dominant allele is present.
A
A
RBC
A
A
A
A
A
A
A
Genotype could be A and A OR A and O
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CB tbl 14.2
What about
RBC
Genotype ??
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CB tbl 14.2
What about
RBC
Genotype OO
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CB tbl 14.2
What about
A
B
RBC
B
A
A
B
B
A
A
B
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CB tbl 14.2
What about
A
B
RBC
B
A
A
B
B
A
A
B
Genotype AB
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Human blood types
CB tbl 14.2
AA or AO
BB or BO
AB
OO
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If Frank has B blood type, his Dad has A blood
type, And his Mom has B blood type Should Frank
be worried?
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
all A / 50 A and 50 O
all B / 50 B and 50 O
Gametes
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
all A / 50 A and 50 O
all B / 50 B and 50 O
Gametes
Frank can be BO B blood
no worries
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Grandparents AB and AB
MomB blood BB or BO
DadA blood AA
possible genotypes
all B / 50 B and 50 O
Gametes
all A
Frank can be BO or BB B blood
Uh-Oh
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Some simple dominant/recessive relationships in
humans
Dom.
Rec.
Rec.
Dom.