Presentation on theme: "Student #1 & Student #2 1 st Period Biology Mr. Teacher."— Presentation transcript:
Student #1 & Student #2 1 st Period Biology Mr. Teacher
Student #1 – blue eyes Father – blue eyesMother – green eyes Paternal Grandparents Grandfather – green eyes Grandmother – blue eyes Maternal Grandparents Grandmother – green eyes Grandfather – brown eyes
Punnett Square for Student #1 Student #1’s Mother has allele combination bbGG and Father has bbgg. Brown/Bluebb bbb b Green/HazelGG gGg g 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.
Father – brown eyes Paternal GrandparentsMaternal Grandparents Mother – blue eyes Student #2 – brown eyes Grandmother – hazel eyes Grandfather – blue eyes Grandmother – brown eyes Grandfather – brown eyes
Punnett Square for Student #2 Student #2’s Mother has allele combination bbgg and Father has BBGG. Brown/Bluebb BBb B Green/Hazelgg GGg G 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.
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: Brown/BlueBb BBBBb b bb Green/Hazelgg GGg ggg 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).
Punnett Square for Potential Offspring See the possible combinations of the two genes (brown/blue, green/hazel): Brown/BlueBb BBBBb b bb Green/Hazelgg GGg ggg 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.
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 Brown/Blue GenePossible Pairs with Green/Hazel BB pairBBGg, BBGg, BBgg, BBgg Bb pair (first)BbGg, BbGg, Bbgg, Bbgg Bb pair (second)BbGg, BbGg, Bbgg, Bbgg bb pairbbGg, bbGg, bbgg, bbgg
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% Total100%
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
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
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%.
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.
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.