Complete question:
1) Inspired by Gregor Mendel, you visit a local greenhouse to see what a pea plant looks like in person. You spot a plant in the corner and immediately notice that it exhibits the purple trait of the flower color character. This character is controlled by one gene with two alleles, the dominant purple P allele, and the recessive white p allele. Identify what you know for certain based on your observation. Check all that apply.
- You know the genotype of the plant.
- This plant has at least one copy of the P allele.
- This plant must be heterozygous with respect to the flower color gene.
- You know the phenotype of the plant.
2) In another corner of the greenhouse, you find another pea plant. This plant, however, exhibits the white trait of the flower color character. The greenhouse plant breeder approaches you and mentions that he plans to cross-fertilize the two plants that you have seen. He offers to let you know how the offspring turn out. Without realizing it, the breeder is actually conducting a
- dihybrid cross
- testcross
- monohybrid cross
3) If you were able to examine hundreds of offspring from this cross, what ratio of purple flowers to white flowers would you observe:
- If the purple parent is PP ---------
- If the purple parent is Pp ----------
4) In a few months, you receive a brief note from the breeder that he checked the four offspring and three have the purple trait and one has the white trait. Since only four offspring were produced, there are not necessarily enough offspring to observe the ratio you predicted. What is the probability of observing three purple and one white offspring:
- If the purple parent is Pp? ----------
- If the purple parent is PP? ----------
5) Based on the four offspring observed, you --------- (can/ cannot) know for certain whether the purple parent is Pp or PP.
Answer:
1)
- This plant has at least one copy of the P allele. Because the plant is purple and the P allele is the one that codifies for this color.
- You know the phenotype of the plant. You can see that the plant has purple flowers, so you know its phenotype regarding flower color.
2) <em>A test cross </em>
3)
- If the purple parent is PP → 1:0 (100% heterozygous purple flowers, Pp)
- If the purple parent is Pp → 1:1 (50% Purple Pp, and 50% white pp)
4)
- If the purple parent is Pp? 3/4 = 75% purple and 1/4 = 25% white
- If the purple parent is PP? 4/4 = 1 = 100% purple and 0 white
5) Based on the four offspring observed, you CAN know for certain that the purple parent is Pp.
Explanation:
Due to technical problems, you will find the complete question, the answer, and the explanation in the attached files.
