Interactive student exploration: inheritance, probability, and Punnett squares.
Student directions: Work through the sections in order. Type your answers directly into the boxes. Use the built-in simulator whenever a question asks you to breed mice or collect offspring data. Your responses save automatically on this device. Use Save responses before leaving, and use Download responses when your teacher asks you to submit your work.
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Vocabulary
allelegenotypephenotypeprobabilityPunnett square
Before you begin: Answer both Prior Knowledge questions without using the simulator. For Question 1, select one answer and click Check. For Question 2, explain your reasoning in complete sentences. After you finish both questions, move to the Warm-up section.
1. A single coin is flipped four times. What do you think is the most likely outcome?
2. What do you think are the odds of getting four tails in a row? Explain your answer.
Gizmo / Simulator Warm-up
Explore phenotype patterns
What to do: Open the Genetics Simulator section below. Choose different parent genotypes and click Breed 1, Breed 100, or Breed 500. Observe the offspring genotypes and phenotypes. Then return here and answer all five questions in complete sentences. Use the dominant/recessive allele information shown in the simulator when explaining your answers.
1. What must be true to have offspring with black fur?
2. What must be true to have offspring with white fur?
3. What must be true to have offspring with black eyes?
4. What must be true to have offspring with red eyes?
5. What must be true to have offspring with red eyes and white fur?
Activity A
Exploring inheritance
Guiding question: What patterns appear when two traits are inherited?
Instructions: Start with a black-fur, black-eye parent and a white-fur, red-eye parent. Use the simulator to produce several offspring. Record the parent genotypes and the offspring genotypes. Next, choose two offspring as the new parents and make a prediction before breeding them. For the final part, produce 100 offspring and record the number in each phenotype category. Do not change your recorded data after you have completed the 100-offspring trial.
1A. What is the genotype of the black-fur, black-eye parent?
1B. What is the genotype of the white-fur, red-eye parent?
1C. What are the genotypes of the offspring?
2. What is the probability that an offspring mouse will have black fur and black eyes?
3. Predict: What do you expect the offspring of the selected mice to look like?
4. Experiment: What genotypes do you see after repeated breeding?
5. After 100 offspring, record your phenotype counts.
Activity B
Probability and genetics
Instructions: Use the parents Ff Ee × Ff ee. First, treat fur color and eye color as two separate one-trait crosses. Complete both 2 × 2 Punnett squares and determine the probability of black fur and the probability of red eyes. Then multiply those two probabilities to predict the chance of an offspring having black fur and red eyes. After making your prediction, use the simulator to breed 500 offspring and compare the experimental percentage with your prediction.
Probability reminder: If two events are independent, the probability that both happen is the product of their separate probabilities.
Parents: Ff Ee × Ff ee
1. Model each trait separately
Fur cross: Ff × Ff
F
f
F
f
Eye cross: Ee × ee
E
e
e
e
2. Multiply the probabilities: black fur AND red eyes
3. After 500 offspring: how many had black fur and red eyes, and what percentage is that?
4. Compare predicted and actual percentages for the other phenotype combinations. Did the method work well?
Activity C
Expanded Punnett square
Guiding question: How can a 4 × 4 square model the inheritance of two traits?
Instructions: Use the cross Ff Ee × Ff Ee. Each parent can produce four gametes: FE, Fe, fE, fe. Fill each cell of the 4 × 4 Punnett square by combining the gamete from the row with the gamete from the column. You may click Generate square from parent gametes after you have attempted the square yourself to check your work. Then calculate the predicted phenotype probabilities. Finally, breed 500 offspring in the simulator, enter the observed results, and compare the experimental results with the predicted ratios.
For Ff Ee × Ff Ee, each parent can pass on FE, Fe, fE, fe.
FE
Fe
fE
fe
FE
Fe
fE
fe
Predicted phenotype probabilities
500-offspring experiment
Trait combination
Black/black
Black/red
White/black
White/red
Number
Percentage
3. Analyze: How well did the results match the predictions of the Punnett square?
4. On your own: Try other parent combinations, predict the phenotype percentages, and test them.
Built-in simulator
Breed two mice
How to use the simulator: Select a genotype for Parent 1 and Parent 2. Click Breed 1 to see one offspring, Breed 100 to add 100 offspring, or Breed 500 to add 500 offspring. The counters show how many offspring fall into each phenotype category. Click Clear before starting a new experiment so results from different crosses are not mixed together. When a worksheet question asks for a specific number of offspring, stop when the total reaches that number.
Trait key:F = dominant black fur, f = recessive white fur; E = dominant black eyes, e = recessive red eyes. A dominant phenotype appears when at least one dominant allele is present.
Latest offspring
No offspring yet.
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Black fur / black eyes
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Black fur / red eyes
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White fur / black eyes
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White fur / red eyes
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Total offspring:0
Before submitting
Final check
Make sure you have: completed every response box, recorded the correct number of offspring for each experiment, compared predictions with experimental results, and entered your name and date. Click Save responses, then Download responses if your teacher requires a file submission.