Biology 1112

1
Lecture 3

• Biology 1112
• January 14, 2002

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Todays Learning Objectives

• Define incomplete dominance
• Be able to
• Perform blood type Punnett Squares
• Perform a dihybrid cross

3
Half Sheet Assessment
4
Biology 1112

• Mr. Chris Kodani
• Office Arts Sciences G-210-E
• Office Hours
• MW 930 to 1130
• TR 1030 to 1130

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Carriers (Review)

• Heterozygous for recessive disorder
• Has just one bad allele
• Asymptomatic (single allele has no effect)

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(No Transcript)
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Early Detection (Review)

• Amniocentesis
• CVS
• Ultrasound

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What to do with Information

• These methods can detect various abnormalities
• If tests positive, then parents can prepare or
  make other choices

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Ethical Question

• Insurance companies dont cover pre-existing
  conditions
• Should it be legal for insurance companies to
  require early detection?
• Should it be legal for insurance companies to
  exclude these children from coverage?

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Incomplete Dominance

• Heterozygotes are intermediate in phenotype
• Hybrid snapdragons have pink flowers (red white
  parents)
• Sickle cell anemia in humans
• 1 copy of allele no anemia, but malaria
  resistant
• 2 copies of allele sickle cell anemia

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3 Alleles ABO Bloodtypes

• Blood cells can have substance A, substance B,
  both, or none
• IA allele for substance A (dominant)
• IB allele for substance B (dominant)
• i allele for no substance (recessive)

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Question

• Little Bobbys blood type is A
• His mom has type O
• What are two possible genotypes for his father?
• Hint
• Punnett Squares
• We get half our alleles from one parent

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7th Inning Stretch
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Dihybrid Cross

• Considers 2 genes
• Gametes still carry only single copy of each gene
• Techniques for Punnett Squares basically same

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Dihybrid Cross Sample Question

• Show the complete set of Punnett squares for this
  cross
• Dihybrid cross of homozygous Round/Yellow with
  Green/Wrinkled
• Yellow Y (capital)
• Round R (capital)

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Go through answer

• On the board

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A WRONG Answer
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Correct Answer
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Question for Thought

• Think of pea plants
• Simple traits
• Easily scored
• Either has, or doesnt)
• How many human traits are simple Mendelian,
  single gene controlled?