Question
Experiment 1: Punnett Square Crosses
In this experiment you will use monohybrid and dihybrid crosses to predict patterns
of inheritance.Procedure:
Part 1: Punnett Squares
1. Set up and complete Punnett squares for each of the following crosses:
(remember Y = yellow, and y = blue)
Y Y and Y yY Y and y y2. What are the resulting phenotypes?3. Are there any blue kernels? How can you tell?4. Set up and complete a Punnett squares for a cross of two of the F1 from Step 1
(above).5. What are the genotypes of the F2 generation?6. What are their phenotypes?7. Are there more or less blue kernels than in the F1 generation?8. Identify the four possible gametes produced by the following individuals:
a) YY Ss:________________________b) Yy Ss:________________________c) Create a Punnett square using these gametes as P and determine the genotypes
of the F1:What are the phenotypes? What is the ratio of those phenotypes?
Part 2 and 3 Setup
1. Use the permanent marker to label the two 100 mL beakers as 1 and 2.
2. Pour 50 of the blue beads and 50 of the yellow beads into Beaker 1. Sift or stir
the beads around to create a homogenous mixture.
3. Pour 50 of the red beads and 50 of the green beads into Beaker 2. Sift or stir
the beads around to create a homogenous mixture.
Assumptions for the remainder of the experiment:
Beaker 1 contains beads that are either yellow or blue.
Beaker 2 contains beads that are either green or red. Both beakers contain approximately the same number of each colored
bead.
These colors correspond to the following traits (remember that Y/y is for
kernel color and S/s is for smooth/wrinkled):
1. Yellow (Y) vs. Blue (y)
2. Green (G) vs. Red (g).
Part 2: Monohybrid Cross
1. Randomly (without looking) take two beads out of Beaker 1. This is the
genotype of Individual #1. Record the genotype in Table 1. Do not put these
beads back into the beaker.
Table 1: Parent Genotypes: Monohybrid Crosses
GenerationGenotype of Individual Genotype of Individual
1
2P
P1
P2
P3
P42. Repeat Step 1 for Individual #2. These two genotypes represent the parents
(generation P) for the next generation.
3. Set up a Punnett square and determine the genotypes and phenotypes for this
cross. Record your data in Table 2
4. Repeat Step 3 four more times (for a total of five subsequent generations).
Return the beads to their respective beakers when finished.
Table 2: Generation Data Produced by Monohybrid Crosses
ParentsPossible
Offspring
GenotypesPossible
Offspring
PhenotypesGenotype RatioPhenotype
RatioP
P1
P2
P3
P4Part 3: Dihybrid Cross
1. Randomly (without looking) remove two beads from of Beaker 1 and two
beads from Beaker 2. These four beads represent the genotype of Individual
#1. Record this information in Table 3
2. Repeat Step 1 to obtain the genotype of Individual #2. Record the phenotypes
of both individuals in Table 3.
Table 3: Parent Genotypes: Dihybrid Crosses
GenerationGenotype of Individual Genotype of Individual
1
2P
P1
P2
P3
P43. Determine what the possible genotypes might be if each individual produced
gametes. Record these possible genotypes in Table 4.
4. Predict the ratio of possible genotypes which could be produced by a cross
between Individual #1 and Individual #2? Record your predictions in Table 4.
Hint: Think back to the example the dihybrid cross in the Introduction. Record
your prediction in Table 2.
5. Set up a Punnett square and determine the genotypes and phenotypes for this
cross.
6. Repeat Step 5 four additional times (for a total of five subsequent
generations).Table 4: Generation Data Produced by Dihybrid Crosses
ParentsP
P1
P2
P3
P4Possible
Offspring
GenotypesPossible
Offspring
PhenotypesGenotype RatioPhenotype
Ratio