Name Date Pd Harry Potter Genetics – Part 3 Incomplete Dominance Use your knowledge of genetics to answer each question. Professor Sprout teaches herbology classes at Hogwarts. One of her favorite plants is the Mandrake. Mandrakes are plants that have a root that looks like a human. The root looks like an infant when the plant is young and matures into an adult as the plant grows older. When the root is unearthed from the ground, it cries like a human. If the root is young, the infant cry, if heard, will knock a person unconscious. The consequences of hearing the cry get worse as the plant matures. Once the root is mature, the cry is fatal to anyone that hears it! Mandrakes can be found in three different colors: yellow, bluish/purple, and green; therefore expressing incomplete dominance. 1. Write the genotypes for each color if Y represents a yellow allele and B represents a blue allele. Yellow = Blue = Green = 2. Professor Sprout crosses a yellow Mandrake with a blue Mandrake. Complete a Punnett square to help you answer the questions. a. List the possible genotypes and phenotypes for the young sprouts. b. What are the chances of a yellow Mandrake? out of or % c. What are the chances of a blue Mandrake? out of or % d. What are the chances of a green Mandrake? out of or % 3. Professor Sprout crosses two green Mandrakes. Complete a Punnett square to help you answer the questions. a. List the possible genotypes and phenotypes for the young sprouts. b. What are the chances of a yellow Mandrake? out of or % c. What are the chances of a blue Mandrake? out of or % d. What are the chances of a green Mandrake? out of or % 4. Professor Sprout crosses a green Mandrake with a yellow Mandrake. Complete a Punnett square to help you answer the questions. a. List the possible genotypes and phenotypes for the young sprouts. b. If Professor Sprout planted 100 seeds from this cross, how many Mandrakes should she expect to have of each color? Yellow – Blue – Green –
The Correct Answer and Explanation is:
. Genotypes for Each Color
Incomplete dominance means neither allele is completely dominant. The heterozygous genotype will have a blended phenotype.
- Yellow =
YY - Blue =
BB - Green (blend of yellow and blue) =
YB
2. Cross: Yellow (YY) x Blue (BB)
Punnett Square:
| B | B | |
|---|---|---|
| Y | YB | YB |
| Y | YB | YB |
a. Possible Genotypes and Phenotypes:
- Genotypes: 100% YB
- Phenotypes: 100% Green
b. Chances of Yellow:
- 0 out of 4, or 0%
c. Chances of Blue:
- 0 out of 4, or 0%
d. Chances of Green:
- 4 out of 4, or 100%
3. Cross: Green (YB) x Green (YB)
Punnett Square:
| Y | B | |
|---|---|---|
| Y | YY | YB |
| B | YB | BB |
a. Genotypes and Phenotypes:
YY= YellowBB= BlueYB(or BY) = Green- Genotypes: 1 YY, 2 YB, 1 BB
- Phenotypes: 1 Yellow, 2 Green, 1 Blue
b. Chances of Yellow:
- 1 out of 4, or 25%
c. Chances of Blue:
- 1 out of 4, or 25%
d. Chances of Green:
- 2 out of 4, or 50%
4. Cross: Green (YB) x Yellow (YY)
Punnett Square:
| Y | Y | |
|---|---|---|
| Y | YY | YY |
| B | YB | YB |
a. Genotypes and Phenotypes:
YY= YellowYB= Green- Genotypes: 2 YY, 2 YB
- Phenotypes: 2 Yellow, 2 Green
b. If Professor Sprout planted 100 seeds:
- Yellow = 50
- Green = 50
- Blue = 0
Explanation:
Incomplete dominance is a type of genetic inheritance in which neither allele is completely dominant over the other. Instead of one trait masking the other, the heterozygous genotype results in a blend of the two parental traits. In the case of Professor Sprout’s Mandrakes, color is determined by two alleles: yellow (Y) and blue (B). When these alleles are inherited together (YB), the Mandrake appears green, a combination of the two parent colors.
The first cross between a yellow (YY) and a blue (BB) Mandrake results in all green (YB) offspring. This is because each parent contributes one allele, and every offspring inherits one Y and one B, making them all green.
When two green Mandrakes (YB x YB) are crossed, the offspring exhibit a classic 1:2:1 genotype ratio. This results in one yellow (YY), two green (YB), and one blue (BB) Mandrake, translating into a 25% chance each of yellow and blue, and 50% chance of green.
In the final scenario, a green Mandrake (YB) is crossed with a yellow one (YY). Half the offspring inherit two yellow alleles (YY), and half inherit one yellow and one blue (YB), making 50% yellow and 50% green. Since no offspring inherit two blue alleles (BB), there are no blue Mandrakes from this cross.
This understanding of incomplete dominance helps Professor Sprout predict the outcomes of her plant breeding and manage her greenhouse effectively, especially when dealing with magical plants as dangerous and sensitive as Mandrakes.
