Name
Block
Date
Crosses Involving Two Traits
-
Predict
produced by two parents, when studying
(genes)
o Example –
-
and
Law of
:
o Two genes will be

separately (
Example –
of one another)
does not depend on eye color
o Any
is possible for the two traits
Performing Genetic Crosses
-
Two trait crosses (
Crosses)
1. Determine
of parents – There will be a total of
for each parent (2 for each gene)

Example:
Seed color:
G=
g=
Stem height:
T=
t=

First parent: Homozygous green seed, short plant =

Second parent: Heterozygous green seed, homozygous tall plant =

Cross =
2. Determine

Each gamete will have

A maximum of

Use FOIL:

Example
 Alleles for GGtt

for gene, or
Ex: One T and one G


produced by each parent
Alleles for GgTT
of alleles are possible
total alleles
3. Set up Punnett Square

Each set of
one trait crosses

When filled in, each box should include


should be placed at each column or row, similar to
(two for each gene)
Arrange alleles in
– G’s together, and T’s together
Example:
GGtt x GgTT
4. Determine
(Genotype ratios aren’t needed)
possible phenotype combinations:






Ratio setup:


The ratio should add up to
(for the 16 boxes in Punnett Square)
Example:

Determine the phenotype ratio for the Punnett Square above:
o P–
Practice:
- For each problem, determine the gametes formed by each parent, and complete the Punnett
Square. Report your results by giving the phenotype ratios for the possible offspring produced
by each cross. Be sure to give the genotypes of the parents if not already given.
Genes:
o Seed color - G = Green, g = yellow
o Plant height - T = tall, t = short
o Flower position - A = axial, a = terminal
o Pod shape - I – inflated, i = constricted
1. Cross the parents below:
Ggtt x GGTt
a. What is the phenotype of the parent that is Ggtt?
b. What is the phenotype of the offspring that is GGtt?
2. Cross the parents below:
AaII x AaIi
a. What is the phenotype of the parent that is AaIi?
b. What is the phenotype of the offspring that is AAIi?
3. Cross a plant that is homozygous tall, heterozygous inflated pod, with a plant that is short,
constricted pod.
4. Cross two plants that are heterozygous tall, heterozygous green seeded.