Dihybrid Crosses
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![Page 1: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/1.jpg)
Dihybrid Crosses
![Page 2: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/2.jpg)
Two characteristics at once…• Dihybrid crosses are where we consider heredity
in two characteristics at the same time.• There are four possible combinations of two
characteristics. Example: Pea color and shape. Peas can be...
• 1) round and yellow
• 2) round and green
• 3) wrinkled and yellow
• 4) wrinkled and green
![Page 3: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/3.jpg)
Phenotype Round, yellow Wrinkled, green
Genotype RRYY rryy
Gametes all RY all ry
F1 all RrYy
All in F1 generation are heterozygous for both characteristics (all round and yellow)
X
P generation cross…
![Page 4: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/4.jpg)
Phenotype Round, yellow
Genotype RrYy
Gametes RY, Ry, rY, ry
F2 We really need a punnet square for this…
X Round, yellow
RrYy
RY, Ry, rY, ry
F1 generation cross…
![Page 5: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/5.jpg)
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
![Page 6: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/6.jpg)
F2 generation ratio
9 3 3 1: : :Round
Yellow
Round
Green
Wrinkled
Yellow
Wrinkled
Green
This is the typical ratio expected in an F1 dihybrid
cross
![Page 7: Dihybrid Crosses](https://reader035.fdocuments.net/reader035/viewer/2022072015/56812fec550346895d9561ea/html5/thumbnails/7.jpg)
Now for trihybrid Crosses...?