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Dihybrid Cross

Dihybrid Cross. Two Traits In this case seed shape and seed color SSYY x ssyy A genetic cross yielding a 9:3:3:1 ratio of offspring. Dihybrid. A dihybrid cross involves a study of inheritance patterns for organisms differing in two traits. Dihybrid.

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Dihybrid Cross

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  1. Dihybrid Cross • Two Traits • In this case seed shape and seed color • SSYY x ssyy • A genetic cross yielding a 9:3:3:1 ratio of offspring.

  2. Dihybrid • A dihybrid cross involves a study of inheritance patterns for organisms differing in two traits.

  3. Dihybrid • Mendel invented the dihybrid cross to determine if different traits of pea plants, such as flower color and seed shape, were inherited independently.

  4. Dihybrid Cross • Determine 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.

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

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

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

  8. Fill out the squares with the alleles of Parent 1. The result is the prediction of all possible combinations of genotypes for the offspring of the dihybrid cross, SsYy x SsYy. Fill out the squares with the alleles of Parent 1.

  9. Spherical, yellow phenotype There are 9 genotypes for spherical, yellow seeded plants. They are: SSYY (1/16)SSYy (2/16)SsYY (2/16)SsYy (4/16) Predicting the phenotype of offspring

  10. Spherical, green phenotype Two recessive alleles result in green seeded plants. There are 2 genotypes for spherical, green seeded plants. They are: SSyy (1/16) Ssyy (2/16) Predicting the phenotype of offspring

  11. Dented, yellow phenotype Two 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) Predicting the phenotype of offspring

  12. Dented, green phenotype A ssyy plant would be recessive for both traits. There is only 1 genotypes for dented, green seeded plants. It is: ssyy (1/16) Predicting the phenotype of offspring

  13. A phenotypic ratio of 9:3:3:1 is predicted for the offspring of a SsYy x SsYy dihybrid cross. 9 spherical, yellow A phenotypic ratio of 9:3:3:1

  14. 3 spherical, green A phenotypic ratio of 9:3:3:1

  15. 3 dented, yellow A phenotypic ratio of 9:3:3:1

  16. 1 dented, green A phenotypic ratio of 9:3:3:1

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