How do you do dihybrid genetic problems

Dihybrid CrossProblem 3: A genetic cross yielding a 9:3:3:1 ratio of offspring.Tutorial to help answer the questionWhich of the following genetic crosses would be predicted to give a phenotypic ratio of 9:3:3:1?TutorialPredicting the genotype of offspringDetermine all possible combinations of alleles in the gametes for each parent.Half of the gametes get a dominant S and a dominant Y allele; the other half of the gametes get a recessive s and a recessive y allele.Both parents produce 25% each of SY, Sy, sY, and sy.(Review the tutorials for problems #1 and problem #4 if necessary).Punnett square.

Since each Parent produces 4 different combinations of alleles in the gametes, draw a 4 square by 4 square punnett square.

Gametes from Parent 1

List the gametes for Parent 1 along one edge of the punnett square.

Gametes from Parent 2

List the gametes for Parent 2 along one edge of the punnett square.

Alleles from Parent 1

Fill out the squares with the alleles of Parent 1.

Alleles from Parent 2Fill out the squares with the alleles from Parent 2.The result is the prediction of all possible combinations of genotypes for the offspring of the dihybrid cross, SsYy x SsYy.

Predicting the phenotype of offspring
Spherical, yellow phenotypeThere are 9 genotypes for spherical, yellow seeded plants. They are:SSYY (1/16)
SSYy (2/16)
SsYY (2/16)
SsYy (4/16)Spherical, green phenotypeTwo recessive alleles result in green seeded plants.There are 2 genotypes for spherical, green seeded plants. They are:SSyy (1/16) 
Ssyy (2/16)Dented, yellow phenotypeTwo recessive s alleles result in dented seeded plants.There are 2 genotypes for dented, yellow seeded plants. They are:ssYY (1/16) 
ssYy (2/16)Dented, green phenotypeA ssyy plant would be recessive for both traits.There is only 1 genotypes for dented, green seeded plants. It is:ssyy (1/16)A phenotypic ratio of 9:3:3:1A phenotypic ratio of 9:3:3:1 is predicted for the offspring of a SsYy x SsYy dihybrid cross.
9 spherical, yellow
3 spherical, green 
3 dented, yellow
1 dented, green

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