DIHYBRID CROSSES Dihybrid Cross Is the crossing of
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.
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. )
Setting up the Alleles Possible allele combination for all 4 possible gametes ? ? ? ?
Foil Method Once you know the parents Genotype, you can set up the alleles for the dihybrid punnett cross. Ex: Aa. Bb Using the foil method looks like this… F – O– I – L – First set Outer set Inner set Last set
Foil Method First set – AB First Set Outer set – A b Inner set – a. B Last set – ab Last Set Aa. Bb Inner Set Outer Set
Using number to Identify gametes For the example on the next slide, you see numbers used to help create the gametes 1234 Aa. Bb First Outer Inner Last (1 and 3) (1 and 4) (2 and 3) (2 and 4) AB Ab a. B ab
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 Ff. Hh x Ff. Hh 1234 1 2 34 FH 1, 3 Fh 1, 4 f. H 2, 3 fh 2, 4 FH FFHh Ff. HH 1, 3 Ff. Hh Fh FFHh FFhh Ff. Hh 1, 4 Ffhh f. H Ff. HH 2, 3 Ff. Hh ff. HH ff. Hh fh Ff. Hh Ffhh ffhh 2, 4 ff. Hh
Key F = sharp fangs f = round fangs H = long hair h = short hair FH 1, 3 Ff. Hh x Ff. Hh 1234 1 2 34 Fh 1, 4 f. H 2, 3 fh 2, 4 FH FFHh Ff. HH 1, 3 Ff. Hh Fh FFHh FFhh Ff. Hh 1, 4 Ffhh f. H Ff. HH 2, 3 Ff. Hh ff. HH ff. Hh fh Ff. Hh Ffhh 2, 4 ff. Hh ffhh Genotype FFHH = 1/16 FFHh = 2/16 Ff. HH = 2/16 Ff. Hh = 4/16 FFhh = 1/16 Ffhh = 2/16 ff. HH = 1/16 ff. Hh = 2/16 ffhh = 1/16 Phenotype 9 Sharp fangs, short hair = 3 Round fangs, long hair = 3 Round fangs, short hair = 1 Sharp fangs, long hair =