Crosses 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 ID: 477757
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Slide1
Dihybrid CrossesSlide2
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.Slide3
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.)Slide4
Setting up the Alleles
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Possible allele combination for all 4 possible gametesSlide5
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 setSlide6
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 bSlide7
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) ABOuter (1 and 4) AbInner (2 and 3) aBLast (2 and 4) abSlide8
fh
f
H
Fh
FH
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.
KeyF = sharp fangsf = round fangs
H = long hairh = short hair
FfHh
x
1
2
1
4
3
2
4
3
FfHh
1, 3
2
, 3
1, 4
1, 3
2,
4
2
, 3
1, 4
2
,
4
fh
f
H
Fh
FH
FFHH
FFHh
FfHH
FfHh
FFHh
FFhh
FfHh
Ffhh
FfHH
FfHh
f
fHH
f
fHh
FfHh
Ffhh
ffHh
ffhhSlide9
Key
F = sharp fangs
f = round fangs
H = long hair
h = short hair
1
2
4
3
1
2
4
3
FfHh
x
FfHh
f
h
f
H
Fh
FH
1, 3
2,
4
2
, 3
1, 4
2
, 3
1, 4
1, 3
2
,
4
fh
f
H
Fh
FH
FFHH
FFHh
FfHH
FfHh
FFHh
FFhh
FfHh
Ffhh
FfHH
FfHh
f
fHH
f
fHh
FfHh
Ffhh
ffHh
ffhh
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
f
fhh
= 1/16
Phenotype
Sharp fangs, long hair =
Sharp fangs, short hair =
Round fangs, long hair =
Round fangs, short hair =
9
3
3
1