Download Using a Test Cross to Determine Genotype

Using a Test Cross to Determine Genotype
Suppose you work for a company that sells seeds. You are studying a plant species in which the
dominant phenotype is pink flowers. The recessive phenotype is white flowers. Customers have
been requesting more plants with pink flowers. To meet this demand, you need to determine the
genotypes of some of the plants you are currently working with.
Known information:
 Plant A of the species you are studying has pink flowers
 When plant A is crossed with Plant B of the same species (Plant B has white flowers):
o the offspring of the cross yields 6 plants with pink flowers and 6 plants
with white flowers
Procedure:
Use Punnett squares to determine the genotype of Plant A, and the answer the questions that
follow.
1. What is the genotype of Plant A? Explain how you arrived at your answer.
2. What are the possible genotypes and phenotypes of offspring if Plant A is crossed with a
plant that is homozygous dominant? Show how you arrived at your answer by using a
Punnett square.
3. What ratio of dominant to recessive phenotypes would exist if Plant A was crossed with a
plant that is heterozygous. Show how you arrived at your answer by using a Punnett
square.
4. Is Plant A the best plant, in terms of genotype, you can work with to produce as many of
the requested seeds as possible? Why or why not? Which genotype would be best to work
with?