Inheritance of Two Traits: Dihybrid Crosses

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Inheritance of Two TraitsDihybrid Crosses
Learning goal Predict the inheritance patterns
and combinations of alleles in gametes of
individuals heterozygous for two traits.
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• Determine the inheritance of two traits
• Two traits in pea plants are seed shape and seed
  color.
• R is the allele for the dominant, round shape
  characteristic
• r is the allele for the recessive, wrinkled shape
  characteristic.
• Y is the allele for the dominant, yellow color
  characteristic
• y is the allele for the recessive, green color
  characteristic.

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Distribution of alleles in gametes

• Assortment of Rr alleles
• The gametes from the RrYy parent will receive one
  of the two alleles Rr.
• Half will receive the dominant R allele, and half
  the recessive r allele.

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Distribution of alleles in gametes

• Assortment of Yy alleles
• The gametes from the RrYy parent will also
  receive one of the two alleles Yy.
• Half will receive the dominant Y allele, and half
  the recessive y allele.

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FOIL to determine gametes

• A quick way to determine the possible gametes
  (R r) (Y y)
• F.irst of each set i RY
• O.uter allele of each Ry
• I.nner allele of each rY
• L.ast allele of each ry
•  
• These combinations of alleles will go in the rows
  or columns of your dihybrid Punnett square

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Draw your Dihybrid Punnett Square
1. Draw a rectangular box 2. Cut the box in
half 3. Cut each half in half
4. Cut in half the other way   5. Cut each of
those in half Now youre ready to set up the
cross RrYy x RrYy
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Dihybrid Cross
F RY
O Ry
I rY
L ry
RY
Ry
rY
ry
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Dihybrid Cross
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Dihybrid Cross