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Checking a probability from a Punnett square
- biology
- intermediate
- 11-13
A student states the chance that offspring show the dominant characteristic; the learner completes the Punnett square in their head and decides whether the claim is true. Three crosses appear, each with a true and a false claim, so the answer cannot be guessed from the picture alone.
Sample question
Two pea plants are crossed: **AA × Aa**. Capital A is the dominant allele for purple flowers and lower-case a is the recessive allele for white flowers. <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 360 80" width="360" height="80" role="img" aria-label="Key to the two alleles"><title>Key to the two alleles</title><g fill="none" stroke="currentColor" stroke-width="1.5"><circle cx="40.0" cy="25.0" r="10" fill="currentColor" fill-opacity="0.45"/><circle cx="54.3" cy="35.4" r="10" fill="currentColor" fill-opacity="0.45"/><circle cx="48.8" cy="52.1" r="10" fill="currentColor" fill-opacity="0.45"/><circle cx="31.2" cy="52.1" r="10" fill="currentColor" fill-opacity="0.45"/><circle cx="25.7" cy="35.4" r="10" fill="currentColor" fill-opacity="0.45"/><circle cx="40" cy="40" r="5"/><circle cx="220.0" cy="25.0" r="10"/><circle cx="234.3" cy="35.4" r="10"/><circle cx="228.8" cy="52.1" r="10"/><circle cx="211.2" cy="52.1" r="10"/><circle cx="205.7" cy="35.4" r="10"/><circle cx="220" cy="40" r="5"/></g><text x="76" y="36" font-size="15" font-weight="700" fill="currentColor">A</text><text x="76" y="54" font-size="12" fill="currentColor">purple, dominant</text><text x="256" y="36" font-size="15" font-weight="700" fill="currentColor">a</text><text x="256" y="54" font-size="12" fill="currentColor">white, recessive</text></svg> A student claims that the probability of an offspring having **purple flowers** is: P(\text{purple}) = 1 Is the claim true or false?
Answer: true