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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Check for UnderstandingSpongebob and his
friend, Patrick, love to go jellyfishing at
jellyfish fields! The fields are home to a
special type of green jellyfish known as Goobers.
Many of the Jellyfish are yellow (YY) or blue
(BB), but some end up green because of incomplete
dominance. What is the genotype of a Goober
green jellyfish?
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What would happen if Spongebob and Patrick
crossed two Goober green jellyfish? Complete
the punnett square to determine the offspring
phenotypes.
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What would happen if they crossed a yellow
jellyfish (YY) with a Goober green jellyfish?
Complete the punnett square to determine the
color of the offspring.
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Codominance

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

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Check for UnderstandingHow is codominance
different from incomplete dominance?
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In some cats, the gene for fur color is
codominant. The allele for black is B and the
allele for orange is O. The heterozygous
phenotype is known as calico.What is the
genotype for black cats?What is the genotype for
orange cats?What is the genotype for a calico
cat?
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If two calico cats were crossed, what is the
probability of having an all black kitten? Use
the punnett square to determine the probability.
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Multiple-Allele Traits

• 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
                                                                                             
(not actual shape or size of antigens)
                                                                                             
(not actual shape or size of antigens)
                                                                                             
(not actual shape or size of antigens)

• 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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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, so
  sex-linked genes are always carried on the X.

• 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 with Hemophilia
• Male genotype with Hemophilia

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Colorblindness

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

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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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• Check for Understanding
• A woman who is heterozygous for normal vision
  (XBXb) marries a man who is colorblind (XbY).
  What are the chances of them having a son or
  daughter who is colorblind? Remember
  Colorblindness is a recessive trait.

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

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Sources credited to castle High School john
hopkins medical institute