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Eye Color Genetics Project

Eye Color Genetics Project. Student #1 & Student #2 1 st Period Biology Mr. Teacher. Student #1 – blue eyes. Father – blue eyes. Mother – green eyes. Paternal Grandparents. Maternal Grandparents. Grandfather – green eyes. Grandmother – green eyes. Grandmother – blue eyes.

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Eye Color Genetics Project

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  1. Eye Color Genetics Project Student #1 & Student #2 1st Period Biology Mr. Teacher

  2. Student #1 – blue eyes Father – blue eyes Mother – green eyes Paternal Grandparents Maternal Grandparents Grandfather – green eyes Grandmother – green eyes Grandmother – blue eyes Grandfather – brown eyes

  3. Punnett Square for Student #1 Student #1’s Mother has allele combination bbGG and Father has bbgg. So the offspring (Student #1) is bbGg, which should result in hazel eyes. However, the green/hazel gene has incomplete dominance. This means that the expressed phenotype can be anywhere from pure green to dark hazel depending on the genes given by the parents.

  4. Student #2 – brown eyes Father – brown eyes Mother – blue eyes Paternal Grandparents Maternal Grandparents Grandfather – blue eyes Grandmother – hazel eyes Grandfather – brown eyes Grandmother – brown eyes

  5. Punnett Square for Student #2 Student #2’s Mother has allele combination bbgg and Father has BBGG. So the offspring (Student #2) is BbGg, which results in brown eyes. The dominant phenotype here is brown eyes, as every possible combination results in brown eyes.

  6. Punnett Square for Potential Offspring Student #1’s allele combination is bbgg, and Student #2’s allele combination is BbGg. Here is the Punnett Square, and the various combinations follow: Student #1 is homozygous in their gene makeup. Both alleles for each genes are the same (bb and gg). Student #2 is heterozygous in their gene makeup. Student #2 posseses both alleles for each gene (Bb and Gg).

  7. Punnett Square for Potential Offspring See the possible combinations of the two genes (brown/blue, green/hazel): Each brown/blue gene can be paired up with 4 different green/hazel genes. This is repeated with each brown/blue gene. Therefore there are 16 different gene pairs. These are listed on the next slide.

  8. Possible Genotypes • The 4 brown/blue genes we paired are BB, Bb, Bb, and bb. These were taken from the Punnett Square. • Number of Genotypes = 16 • BBGg = 2, BBgg = 2, BbGg = 4, Bbgg = 4, bbGg = 2, bbgg = 2

  9. Genotype Probabilities • Number of Genotypes = 16 • BBGg = 2, BBgg = 2, BbGg = 4, Bbgg = 4, bbGg = 2, bbgg = 2 • Probability of BBGg offspring = 2/16 * 100 = 12.5% • Probability of BBgg offspring = 2/16 * 100 = 12.5% • Probability of BbGg offspring = 4/16 * 100 = 25% • Probability of Bbgg offspring = 4/16 * 100 = 25% • Probability of bbGg offsrping = 2/16 * 100 = 12.5% • Probatility of bbgg offspring = 2/16 * 100 = 12.5% Total 100%

  10. Brown Phenotype Probability • There are 4 genotypes that produce a brown eyed offspring: • BBGg, BBgg, BbGg, Bbgg • Since brown is dominant over all other colors the presence of a big B allele will automatically give the child brown eyes, regardless of the green/blue gene. • Adding the probabilities for each of the genotypes we get the total probability for the phenotype • 12.5% + 12.5% + 25% + 25% = 75% probability of having a brown eyed offspring

  11. Hazel Phenotype Probability • For the green/hazel gene to be shown in a phenotype the brown/blue gene must be bb. • There is one genotype that will give you hazel eyes. Because the gene for green/hazel eyes has incomplete dominance you need a heterozygous genotype for green/hazel to have hazel eyes. • bbGg • Since there is only one genotype for hazel eyes, the probability for the phenotype is the same as the probability for the genotype. • bbGg = 12.5% probability of having a hazel eyed offspring

  12. Green Phenotype Probability The green phenotype requires a genotype of bbGG. Since this genotype is not represented in our hypothetical offspring, the probability of green phenotype is 0%.

  13. Blue Phenotype Probability The only genotype that produces a blue phenotype is bbgg. Because of this the probability of the genotype is the same as the probability of the phenotype. 12.5% probability child will have blue eyes.

  14. Conclusion! It is most probable that if Student #1 and Student #2 were to create an offspring, that offspring would have the phenotype of brown eyes. It is impossible for their offspring to have green eyes.

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