Incomplete Dominance

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Incomplete Dominance
Neither allele is dominant
Phenotype of heterozygote is intermediate between
the two homozygotes
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X
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Co-dominance -both alleles are present in their
full form in the heterozygote
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AA AB BB
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Blood
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Composition of blood
White blood cells
Red blood cells
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Red blood cells have antigens along their surface
that function in recognition
These antigens have a specific shape
Which shape you have is inherited from your
parents
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The A allele ( IA) says to make at place A
antigens on your red blood cells
The B allele ( IB) says to make at place B
antigens on your red blood cells
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What if you have an A allele and a B allele?
The A and B allele are CODOMINANT
Both are equally expressed in the phenotype
What about the other blood type?
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The i allele says dont put any antigens on the
red blood cells and is recessive to both IA and IB
This is an example of MULTIPLE ALLELES
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Type O
Phenotype Antigens on red blood cells
Type A
Type B
Type AB
Possible Genotypes?
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A man has Type A blood and marries a woman with
Type O blood. The mans father had Type O blood.
What is the chance this couple has a baby with
type O blood?
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A woman who is AB gives birth to a baby who is
A-. The father is B. Give the genotype of mom,
dad, and baby. What is the chance they will
have a B child?
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  ABO Type    Rh Type  How Many Have It  How Many Have It 
O positive   38      45 
O negative 7   45 
A positive 34 40
A negative 6 40
B positive 9 11
B negative 2 11
AB positive 3 4
AB negative 1 4
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Agglutination clumping
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Some traits vary along a continuum
Human skin color
Polygenic Inheritance
More than one gene controls a character
Human skin color 3 genes
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2 plants, same genotype, whats up?
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Corn Genetics
Hypothesis If the parents of cross A are ___ X
___ then,.. (what phenotypic ratios would you
expect)
Procedure Variables not included Data
Table be sure to include expected and actual
values Conclusion/discussion give support for
hypothesis include why the expected
and actual values do not match
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X
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A woman is a carrier for hemophilia (a sex-linked
trait). She marries a normal man. What are the
probabilities of the different phenotypes in her
offspring.
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Autosomal Dominant
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Autosomal Recessive
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X-linked recessive
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Linked Genes

• Found near each other on same chromosome
• Segregate (move) together during meiosis
• Do not follow the ratios expected from
  independent assortment (Mendels second law)
• -Crossing over in prophase one can unlink genes
• Called recombination
• -Further apart they physically are from each
  other, greater the rate of recombination
• Can use these rates to create a map of genes on a
  chromosome

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Tomatoes red fruit is dominant to yellow
tall plants are dominant to short plants
A true-breeding red/tall plants are crossed with
a true-breeding yellow/short plant. What is the
genotype of the F1 generation? If one of these
F1 plants is crossed with a yellow short
plant. What would be the expected phenotypic
ratio if the genes are not linked? What would be
the expected phenotypic ratio if the genes are
completely linked? Actual results Tall/red
487 tall/ yellow 18 short/red
13 short yellow 482 Are the genes linked or
unlinked? If linked, how far away from each
other are they?
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You also have proteins in your plasma called
antibodies that can recognize specific shapes on
cells.
These antibodies bind to their matching antigens
and cause cells to clump
You dont make antibodies against your own
antigens or else you would be attacking yourself
What happens when you get a blood transfusion and
the blood types arent a match?
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