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Dihybrid Cross Notes

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Dihybrid Cross Notes Have your Monohybrid Notes Out! Example Heterozygous, black, hairless male mouse is crossed with a white heterozygous hairy female mouse. – PowerPoint PPT presentation

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Title: Dihybrid Cross Notes


1
Dihybrid Cross Notes
Have your Monohybrid Notes Out!
2
Example
  • Heterozygous, black, hairless male mouse is
    crossed with a white heterozygous hairy female
    mouse.

3
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
1. Determine dominant and recessive traits Will be stated in the problem Black is dominant to white Hairy is dominant to hairless


4
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
2. Assign letters for the trait Dominant trait gets the capital letter Recessive traits gets the lower case letter B black b white H Hairy h hairless


5
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
3. Determine genotype for parents Each parent must have 4 alleles Each parent will have has two alleles for two traits Heterozygous, black, hairless male Bbhh White heterozygous hairy female bbHh


6
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
4a. Draw a 4x4 square There will be 16 boxes total





7
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
4b. Put parent gamete combinations on box Separate parental alleles Think of it like distributing You should have four possible combination Bbhh gametes Bh, Bh, bh, bh bbHh gametes bH, bh, bH, bh


8
  • Step 4b.
  • Bh Bh bh bh
  • bH
  • bh
  • bH
  • bh





9
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
5. Determine genotype of offspring Punnett square holds offspring genotypes Genotype letter code You should have 16 possible offspring

10
  • Step 5.
  • Bh Bh bh bh
  • bH
  • bh
  • bH
  • bh

BbHh BbHh bbHh bbHh
Bbhh Bbhh bbhh bbhh
BbHh BbHh bbHh bbHh
Bbhh Bbhh bbhh bbhh




11
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
5. Determine genotype of offspring Punnett square holds offspring genotypes Genotype letter code You should have 16 possible offspring

12
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
6. Determine genotype ratio Count offspring in the Punnett square You should have 16 possible offspring 4 BbHh 4 Bbhh 4 bbHh 4 bbhh


13
Heterozygous, black, hairless male mouse is
crossed with a white heterozygous hairy female
mouse.
Step Notes Example
7. Determine phenotype ratio Phenotype what they look like You have two traits to describe! ratio MUST add up to the number of boxes 4 Black Hairy 4 Black Hairless 4 White Hairy 4 White Hairless


14
Genotype Practice
  • 1. In bunnies, black is dominant to white. Rough
    is dominant to smooth.
  • Give the genotype for each of the following
  • a. Homozygous black, smooth bunny _____________
  • b. Heterozygous black-rough bunny _____________
  • c. White, homozygous rough bunny _____________
  • d. White, smooth bunny _____________
  • e. Homozygous black-rough bunny _____________
  • f. White, heterozygous rough bunny _____________

15
Gamete Combination Practice
  • 2. Give the gamete combination for each genotype.
  • a. AATt _____, _____, _____, _____
  • b. AaTT _____, _____, _____, _____
  • c. aatt _____, _____, _____, _____
  • d. AAtt _____, _____, _____, _____

16
3. In hamsters, black coat is dominant to white
coat and rough coat is dominant to smooth coat.
Two heterozygous black-rough coated hamsters
where mated.
  • a. Give the genotype cross ____________x_________
    ___
  • b. List the possible gametes formed by each
    parent.
  • ____, ____, _____, _____





17
3. In hamsters, black coat is dominant to white
coat and rough coat is dominant to smooth coat.
Two heterozygous black-rough coated hamsters
where mated.
  • d. What would be the genotype ratio of the F1
    generation?
  • ___ BBRR ___ BBRr ___ BBrr ___ BbRR
  • ___ BbRr ___ Bbrr
  • ___ bbRR ___ bbRr
  • ___ bbrr
  • e. What would be the phenotype
  • ratio of the F1 generation?
  • ____ Black-Rough
  • ____ Black-Smooth
  • ____ White-Rough
  • ____ White-Smooth




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