Question

1. A series of unlinked genes contribute in an equal manner to determine the number of flowers in an inflorescence for a plant species. Two pure breeding lines, one with 4 flowers and a second with 12 flowers per inflorescence. After the cross is performed the F1 plants have 8 flowers per inflorescence. The F1 plants as crossed with each other and the resulting F2 produces plants with as few as 4 flowers per inflorescence and as many as 12.

a. How many classes are present in the F2?

Number of classes =

b. Use the number of classes in the F2 to determine the number of loci that control this trait.

Number of genes =

c. Let’s assume each gene has two alleles. One that adds to the number of flowers (uppercase allele) and one that does not lowercase allele).

How many additive alleles are in plants that have 4 flowers per inflorescence? Write down the genotype. How many additive alleles are in plants that have 12 flowers per inflorescence? Write down the genotype. What is the genotype of the F1?

d. Make a list of the possible gametes the F1 can produce. Group the alleles according to the number of additive alleles in each one.

Number of additive alleles	Gamete(s)
0
1
2
3
4

e. Cross the alleles in part d to obtain the possible F2 phenotypes listed on the table.
For example, plants with 5 flowers per inflorescence have one additive allele producing the phenotype. This phenotype is obtained from the cross between two gametes, one with zero additive alleles and another one with 1 additive alleles.

Number of flowers per inflorescence	Number of additive alleles	Possible genotypes
5	1
6
11
12

f. Use multiplication and addition rules to determine the probability of observing x number of flowers per inflorescence in the F2. Give all your probabilities as fractions of 256.

5 flowers per inflorescence	Genotype	Probability
		total p =

6 flowers per inflorescence	Genotype	Probability
		total p =

11 flowers per inflorescence	Genotype	Probability
		total p =

12 flowers per inflorescence	Genotype	Probability