Predicted vs. Observed Results

1
Predicted vs. Observed Results
2

• Problem How do the predicted results compare
  to the actual results in a genetic cross as the
  sample size increases?
• Background
• Black is dominant fur color in mice, white is
  recessive.
• What is the chance for getting a B or a b in a
  heterozygous mouse?
• Hypothesis

3

• Procedure
• Make a cross of Bb x Bb using a punnett square to
  find the expected results of crossing 2
  heterozygous mice.
• Mark 2 coinsB on one side and b on the other.
  Each coin represents one of the heterozygous
  mice.
• Flip the coins together 40 times, and record the
  results of the offspring in table 1 .
• Calculate the percentage of the resulting
  phenotypes in table 1.
• Repeat steps 1-4 except cross Bb x bb, changing
  one of the coins to b on one side and b on the
  other and use table 2 to record data.

4

• Data

Table 1 BbxBb
Gene combinations BB Bb bb
Total expected in 40 tosses
Total observed in 40 tosses
Phenotype Black Black White
Total expected
Total observed
5
Table 2 Bbxbb
Gene combinations BB Bb bb
Total expected in 40 tosses
Total observed in 40 tosses
Phenotype total Black Black White
6

• spreadsheet

7

• Data Analysis
• If I have a black mouse and I want to find out
  what its genotype is, how could I set up an
  experiment to determine the genotype of the
  mouse?
• How did your expected results compare to your
  observed results?
• How did the class expected results compare to the
  class observed results?
• Explain what each side of the penny represented,
  what the flipping of the penny represented, how
  it relates to the chromosomes, and what the sides
  that were facing up represented.

8

• Conclusion Write a CER paragraph to explain how
  the predicted results compare to the expected
  results as the sample size increases.