Dihybrid CrossProblem 3: A genetic cross yielding a 9:3:3:1 ratio of offspring.Tutorial to help answer the question Which of the following genetic crosses would be predicted to give a phenotypic ratio of 9:3:3:1?
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Since each Parent produces 4 different combinations of alleles in the gametes, draw a 4 square by 4 square punnett square. |
List the gametes for Parent 1 along one edge of the punnett square. |
List the gametes for Parent 2 along one edge of the punnett square. |
Fill out the squares with the alleles of Parent 1. |
Fill 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 phenotype
There are 9 genotypes for spherical, yellow seeded plants. They are:
SSYY (1/16) |
Two recessive alleles result in green seeded plants. There are 2 genotypes for spherical, green seeded plants. They are:
SSyy (1/16)
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Two recessive s alleles result in dented seeded plants. There are 2 genotypes for dented, yellow seeded plants. They are:
ssYY (1/16)
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A 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 9:3:3:1 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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