Question

morning glories can have blue, purple, or red flowers. flower color is controlled by two genes. blue color is produced when at least one dominant allele is present at both genes, a and b. purple flowers result when a dominant allele is present at only one of the two gene loci, a or b. flowers are red when the plant is homozygous for two recessive alleles at each gene (i.e., aabb). two pure - breeding purple strains are crossed, and all the f1 plants have blue flowers. part a: what are the genotypes of the parental plants? check all that apply. aabb, aabb, aabb, aabb, aabb, aabb, aabb, aabb, aabb. part b: if two f1 plants are crossed, what are the expected phenotypes? check all that apply.

Explanation:

Step1: Determine F1 - generation genotype

Two pure - breeding purple strains (homozygous recessive for both genes, aabb) are crossed. The F1 generation is formed by the cross of aabb×aabb, and all F1 plants have the genotype AaBb.

Step2: Analyze parental genotypes

Since the F1 plants have the genotype AaBb and are formed from the cross of two pure - breeding parental plants, and we know that the parental plants are homozygous recessive for both genes to start with, the parental genotypes must be aabb.

for Part B:

Step1: Set up the Punnett - square for F1 cross

When two F1 plants (AaBb) are crossed, the possible gametes from each plant are AB, Ab, aB, and ab. The Punnett - square will have 16 possible combinations.

Step2: Determine phenotypes based on genotypes

Blue color is produced when at least one dominant allele is present at both genes A and B. Purple flowers result when a dominant allele is present at only one of the two gene loci (A or B). Red flowers are when the plant is homozygous for two recessive alleles at each gene (i.e., aabb).
The genotypes and their corresponding phenotypes:

• AABB, AABb, AaBB, AaBb: Blue (dominant alleles at both A and B)
• AAbb, Aabb, aaBB, aaBb: Purple (dominant at one locus only)
• aabb: Red (homozygous recessive at both loci)

Answer:

aabb