Download Name Period _____ Date

Name ____________________________________ Period _____ Date _____________________
GENETICS LAB - PENNY SIMULATION
Procedure – For this activity you will first track a single trait (fur color) and then
you will track 2 traits at same time, fur color and fur length.
Fur color is represented by B = black and b = white.
Fur length is represented by L = long and l = short
Terms
a)
b)
c)
d)
e)
Expected results – Percentages based on probability
Observed results – Actual percentages based on experiment
Homozygous dominant – When both alleles are Dominant (BB)
Homozygous recessive – When both alleles are recessive (bb)
Heterozygous – when there is a recessive and dominant allele (Bb)
Hypothesis: Will your observed results be the same or similar as your expected results? If you
increase the number of times you do a cross, do you expect the expected and observed results to
become more similar or more different? Write hypothesis here:
Procedure:
Each group will need 5 pennies. Put a small piece of tape on each side of each penny. Then label
1) On 2 pennies, write a B on one side and b on other side.
2) On 1 penny place a small b on BOTH sides.
3) On 2 pennies write L on one side and l on other side.
Pennies will be Bb and Bb
Penny will be bb
Pennies will be Ll and Ll
Expected Results Part I Heterozygous cross
For a cross between a female mouse who is heterozygous (Bb) for fur color and a male mouse
who is also heterozygous for fur color (Bb) (B=Black; b=white ) create a punnet square
1) Expected results:
Percent BB ___________ color ______________
Percent Bb ___________ color ______________
Percent bb ___________ color ______________
2) What percent of the offspring do you expect to have the dominant color? _________
Observed Results Part I: Heterozygous cross
a) Take the 2 pennies marked B on one side and b on the other
b) Toss them together and record your observed results on table below using a slash mark /
to indicate which combination was observed. Repeat 40 times, marking box each time.
c) Count the total marks in each column and write total in total observed box
d) Using the expected results from number 3 above, fill in the expected totals based on
probability. Multiply the percent expected by 40 to find expected results for 40 crosses.
e) Record the color of each cross in last box of column
Gene combinations
BB
Bb
bb
Observed results
Total observed
in 40 tosses
Total expected
in 40 tosses
Mouse fur color
(phenotype)
Expected results part II - Heterozygous crossed with homozygous recessive.
Cross a female mouse heterozygous (Bb) for fur color with a male that is homozygous recessive
(bb) for fur color and fill in punnet square below
3) Expected results:
Percent BB ___________ color ______________
Percent Bb ___________ color ______________
Percent bb ___________ color ______________
4) What percent of the offspring do you expect to have the dominant color? _________
Observed results part II - Heterozygous crossed with homozygous.
a) Take one penny marked both B and b and the one penny marked b on both sides (bb)
b) Toss both pennies at same time and record results with a slash mark ( / ) in the proper
observed results column below
c) Add up total marks for each combination and enter total in total observed boxes
d) Using percents calculated under expected results (#2 above) , multiply the expected
results percent by 40 to get the number expected for each combination
e) Record the coat color of each combination in last row
Gene combinations
BB
Bb
bb
Observed results
Total observed
in 40 tosses
Total expected
in 40 tosses
Mouse fur coat color
(phenotype)
Expected results Part III - DIHYBRID CROSS –ALL homozygous
5) First - Cross a mouse that is pure homozygous dominant for both traits with a mouse
homozygous recessive for both traits
(BBLL x bb l l) P1 generation
BL
bl
BL
BbLl
bl
6) Second - Now cross 2 of the offspring from above F1 generation (BbLl x BbLl)
When both parents are heterozygous for both traits it is called a dihybrid cross
BL
BL
Bl
bL
bl
Bl
bL
bl
BBLL
BbLl
7) The results of the dihybrid Punnet square are the F2 generation
Fill in table below to determine frequencies for genotype and phenotype expected
Genotype
Genotype frequency
Phenotype
Phenotype frequency
(n/16)
Ratio (n/16)
BBLL
1/16
Black Long
BBLl
BbLL
BbLl
BBl l
3/16
Bbl l
bbLL
bbLl
Bbl l
Observed Results Part III - DIHYBRID CROSS Both heterozygous for both traits
8) You will be testing a dihybrid cross of mice that are both heterozygous for fur color and
fur length. For this cross you need the 2 Bb coins and the two Ll coins. This time you will
be doing 100 crosses so you will be flipping coins 100 times. You will need 3 students,
two flippers and one recorder.
Student #1 Coin flipper tosses two coins Bb and Bb representing fur color genes.
Student #2 coin flipper tosses two coins Ll and Ll representing fur length genes.
Student #3 Recorder. Records resulting phenotypes and keeps count of crosses
After 100 tosses, total each type and then calculated the observed ratio by dividing the
number observed for each phenotype by 100. (move decimal two places left. Then multiply
by 16 to get ratio out of 16. Round to nearest whole number. Fill in the expected ratios you
calculated in table 7 and compare. Enter your group totals on board. Divide by total class
tosses and multiply by 16
Observed results tally
observed
100 tosses
Observed
Ratio
obs. X 16
100
Expected
Ratio
(get from
table 7)
Black and Long
BB or Bb & LL or Ll
Black and short
BB or Bb & l l
White and Long
bb & Ll or LL
White and short
bb & l l
Class results
Phenotypes
group totals
Group
1
Black and Long
Black and short
white and Long
white and short
Group
2
Group
3
Group
4
Class
totals
Group
5
Group
6
Observed
class ratio
Analysis questions
1. Which traits were dominant? How do you know? ___________________________________
2. Which were recessive? How do you know? _________________________________________
3. What percent of the time would you expect a coin toss to land on heads? _______________
How is a coin toss similar to how genes are passed from parents to offspring?
4. What is the chance that an individual will give a recessive gene to its offspring if an individual
is heterozygous for that trait? ________ What is the chance that an individual will give a
recessive gene to its offspring if an individual is homozygous recessive for a trait? _______
5. For part I, how close were your observed results to your expected results? Describe your
data.
6. For part II how close were your observed to expected results? Describe your data.
7. For Part III, Dihybrid cross, how close was your group’s results to expected results?
Were your group results perfectly 9:3:3:1?
8. Compare your group ratios to the other group ratios and the class ratio? Which was closer to
the expected ratio? Explain and relate to your hypothesis.
Conclusion – 12 point writing rubric
Write a conclusion that begins with your hypothesis about observed vs. expected results and
then describe how you used coins to test your hypothesis and what the outcomes were. Use the
information from the analysis above in your written discussion.