Non-Mendelian Genetics

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Non-Mendelian Genetics
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Non-Mendelian Genetics

• Some traits dont follow the simple
  dominant/recessive rules that Mendel first
  applied to genetics.
• Traits can be controlled by more than one gene.
• Some alleles are neither dominant nor recessive.

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Incomplete Dominance

• One allele is not completely dominant over
  another.
• The heterozygous phenotype is a blending of the
  two homozygous phenotypes.
• Example four oclock flowers
• rrred
• wwwhite
• rwpink (blending of the two alleles)

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Codominance

• Two alleles are both expressed as a dominant
  phenotype
• Coat color in cows
• RR Red
• WW White
• RW Roan, white with red spots (NOT pink!)

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Multiple-Allele Series

• Codominance
• More than two choices of alleles are present for
  a trait
• ABO blood type has three alleles
• ABO Blood types
• If both A and B are present, type is AB
• Neither is recessive
• Individuals can be type A, B, AB, or O
  (recessive)

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What is blood made up of?

• The red blood cells
• contain hemoglobin.
• Red blood cells transport O2 and CO2 to and from
  body tissues.
• The white blood cells
• fight infection.
• The platelets
• help the blood to clot
• The plasma
• Fluid which contains salts and various kinds of
  proteins.

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Determining Blood Type

• Protein molecules found on the surface of RBCs
  and in the blood plasma determine the blood type
  of an individual.
• Antigens are located on the surface of the red
  blood cells
• Antibodies are in the blood plasma.

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What are the different blood groups?

• Blood group A (IA, IA ), (IA, i) have A antigens
  on the surface of red blood cells and B
  antibodies in blood plasma.
• Blood group B (IB, IB ), (IB, i)
• have B antigens on the surface of red blood
  cells and A antibodies in blood plasma.

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What are the different blood groups?

• Blood group AB (IA, IB )
  have both A and B antigens on the
  surface of red blood cells and no A or B
  antibodies in blood plasma.
• Blood group O (i, i)
  have neither A or B antigens on the surface
  of red blood cells but have both A and B
  antibodies in blood plasma.

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Blood transfusions who can receive blood from
whom?

• The transfusion will work if a person who is
  going to receive blood has a blood group that
  doesn't have any antibodies against the donor
  blood's antigens.

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• People with blood group 0 are called "universal
  donors" and people with blood group AB are called
  "universal receivers."

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Rh Factor

• Refers to another antigen on red blood cells
• Dominant trait is to have the antigen
• Rh
• Recessive trait is not to have it
• Rh-
• A person with Rh- blood will produce antibodies
  to Rh blood
• Can be a problem in pregnancy

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Sex-Linked Inheritance
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Review

• Males have an X and a Y chromosome
• Females have two X chromosomes
• These chromosomes determine sex, so genes located
  on these chromosomes are known as sex-linked
  genes.

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• The X chromosome is much larger than the Y, so it
  carries more genes than the Y chromosome.

• Disorders that are sex-linked are much more
  common in males, because they would only need 1
  recessive allele to have the trait rather than
  the two recessive alleles the females need.

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Hemophilia

• Recessive trait
• Disorder where individuals are missing the normal
  blood clotting protein.
• Uncontrolled bleeds from minor cuts or bruises.
• Female genotype
• Male genotype

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Colorblindness

• Recessive
• Inability to see certain colors
• Female genotype
• Male genotype

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Duchenne Muscular Dystrophy

• Recessive
• Progressive weakening and loss of skeletal
  muscle.
• Defective version of gene that codes for muscle
  protein
• Female genotype
• Male genotype

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• EXAMPLES!!
• A woman who is heterozygous for normal vision
  marries a man who is colorblind. What are the
  chances of them having a son or daughter who is
  colorblind?
• NOTE You have to use Xs and Ys, and read
  the punnett square separately for boys and
  girls!

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• A woman who is homozygous for normal blood
  clotting marries a man who has hemophilia. What
  are the chances of them having a son or daughter
  with hemophilia?