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Objectives
1. Define Dihybrid Inheritance and Law of
Independent Assortment.
2. How did Gregor Mendel conduct his
experime...
Law of Independent Assortment
• States those alleles of different genes assort
independently of another during gamete
form...
Dihybrid Inheritance
• Refers to the simultaneous inheritance of two
characters
• For example, Mendel crossed plants that
...
Mendel’s Experiment
• Mendel investigated the inheritance of seed
shape (round or wrinkled) and seed color (green
or yello...
Problem Solving for Dihybrid Cross
1. Predicting the genotype of offspring
• Determine all possible combinations of allele...
2. Punnett Square
• 4x4 square panel
• Since each Parent produces 4 different
combinations of alleles in the gametes, draw...
3. Gametes from Parent 1
• List the gametes for Parent 1along one edge of
the punnett square.
4. Gametes from Parent 2
• List the gametes for Parent 2along one edge of
the punnett square.
5. Alleles from Parent 1
• Fill out the squares with the alleles of Parent
1.
6. Alleles from Parent 2
• Fill out the squares with the alleles
from Parent 2.
• The result is the prediction of all poss...
Predicting the phenotype of offspring
• Spherical, yellow phenotype
- There are 9 genotypes for spherical, yellow
seeded p...
•Spherical, green phenotype
- Two recessive alleles result in green seeded
plants.
- There are 2 genotypes for spherical, ...
Dented, yellow phenotype
- Two recessive s alleles result in dented
seeded plants.
- There are 2 genotypes for dented, yel...
Dented, green phenotype
- A ssyy plant would be recessive for both
traits.
- There is only 1 genotypes for dented, green
s...
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  1. 1. Objectives 1. Define Dihybrid Inheritance and Law of Independent Assortment. 2. How did Gregor Mendel conduct his experiments which led to the formulation of the 2nd law? 3. How does one solve a problem on dihybrid inheritance using the punnet square?
  2. 2. Law of Independent Assortment • States those alleles of different genes assort independently of another during gamete formation. • One gene determines flower color, a second gene determines the length of stem, a third gene determines shape of pods, and so on.
  3. 3. Dihybrid Inheritance • Refers to the simultaneous inheritance of two characters • For example, Mendel crossed plants that varied in both seed shape and seed color
  4. 4. Mendel’s Experiment • Mendel investigated the inheritance of seed shape (round or wrinkled) and seed color (green or yellow) at the same time. • From his monohybrid crosses he knew that round seeds were dominant to wrinkled seeds and yellow seeds were dominant to green seeds. • He chose to cross plant that were pure breeding for both dominant features (round and yellow seeds) with plants that were pure breeding for both recessive features (wrinkled and green seeds).
  5. 5. Problem Solving for Dihybrid Cross 1. Predicting the genotype of offspring • 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 gets a recessive s and a recessive y allele. • Both parents produce 25% each of SY, Sy, sY, and sy.
  6. 6. 2. Punnett Square • 4x4 square panel • Since each Parent produces 4 different combinations of alleles in the gametes, draw a 4 square by 4 square punnett square.
  7. 7. 3. Gametes from Parent 1 • List the gametes for Parent 1along one edge of the punnett square.
  8. 8. 4. Gametes from Parent 2 • List the gametes for Parent 2along one edge of the punnett square.
  9. 9. 5. Alleles from Parent 1 • Fill out the squares with the alleles of Parent 1.
  10. 10. 6. Alleles from Parent 2 • 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.
  11. 11. Predicting the phenotype of offspring • 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)
  12. 12. •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)
  13. 13. 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)
  14. 14. 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)

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