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Biology · Grades 9–12

Expected counts in Aa × Aa

For the simple Aa × Aa model, P(aa) = 1/4. An expected count is not a guaranteed outcome in a finite sample.

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Rule and assumptions

For the simple Aa × Aa model, P(aa) = 1/4. An expected count is not a guaranteed outcome in a finite sample.

expected aa count = offspring count × 1/4

Worked examples

In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 468 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

expected aa count = offspring count × 1/4 468 × 1/4 = 117

117

In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 332 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

expected aa count = offspring count × 1/4 332 × 1/4 = 83

83

Try two questions

  1. In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 340 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

  2. In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 548 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

Answers and reasoning

Answers and marking notes
  1. 85

    expected aa count = offspring count × 1/4 340 × 1/4 = 85

  2. 137

    expected aa count = offspring count × 1/4 548 × 1/4 = 137

Further reading and review references

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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.