1. DIHYBRID CROSSES

2. Dihybrid Cross  Is the crossing of two traits.  Instead of looking at probability of inheriting 1 traits, we are now going to analyze inheriting 2 traits.

3. Setting up the Parent Alleles  Remember: every trait in a dihybrid cross has 2 alleles (one from each parent)  When setting up a dihybrid cross make sure each possible gamete has 2 alleles (one for each trait.)

4. Setting up the Alleles ???? ? ? ? ? Possible allele combination for all 4 possible gametes

5. Foil Method  Once you know the parents Genotype, you can set up the alleles for the dihybrid punnett cross.  Ex: AaBb  Using the foil method looks like this… F – First set O – Outer set I – Inner set L – Last set

6. Foil Method A a B b First Set Last Set Inner Set Outer Set First set – A B Outer set – A b Inner set – a B Last set – a b

7. Using number to Identify gametes  For the example on the next slide, you see numbers used to help create the gametes 1 2 3 4 A a B b First (1 and 3) AB Outer (1 and 4) Ab Inner (2 and 3) aB Last (2 and 4) ab

8. fhfHFhFH 1. In werewolves, sharp fangs are dominant (F) and round fangs are recessive (f). Long hair is dominant (H) and short hair is recessive (h). Cross a heterozygous sharp fanged, hybrid long haired werewolf with a hybrid sharp fanged, heterozygous long haired werewolf. Give the genotypic and phenotypic percentage and ratios of the F 1 offspring. Key F = sharp fangs f = round fangs H = long hair h = short hair FfHh x 12143243 FfHh 1, 3 2, 3 1, 4 1, 3 2, 42, 31, 4 2, 4 fh fH Fh FHFFHHFFHhFfHHFfHh FFHhFFhhFfHhFfhh FfHHFfHhffHHffHh FfHhFfhhffHhffhh

9. Key F = sharp fangs f = round fangs H = long hair h = short hair 12431243 FfHh xFfHh fhfHFhFH 1, 32, 42, 31, 4 2, 3 1, 4 1, 3 2, 4 fh fH Fh FHFFHHFFHhFfHHFfHh FFHhFFhhFfHhFfhh FfHHFfHhffHHffHh FfHhFfhhffHhffhh Genotype FFHH = 1/16 FFHh = 2/16 FfHH = 2/16 FfHh = 4/16 FFhh = 1/16 Ffhh = 2/16 ffHH = 1/16 ffHh = 2/16 ffhh = 1/16 Phenotype Sharp fangs, long hair = Sharp fangs, short hair = Round fangs, long hair = Round fangs, short hair = 9 3 3 1