Chance of tt from Tt × Tt?
Reveal answer
1 in 4 (25 %).
Key words: 25
4(b) INHERITANCE · RECALL
4.25 Probabilities from monohybrid crosses
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Why does each child have the same chance?
Reveal answer
Each fertilisation is random and independent.
Key words: independent
Chance a child of Tt × Tt shows the dominant phenotype?
Reveal answer
3 in 4 (75 %).
Key words: 75
What is meant by the term probability?
Reveal answer
Numerical measure from 0 to 1 of how likely an outcome is.
Key words: probability
What is meant by the term independent event?
Reveal answer
Event whose outcome does not alter the probability of the next event.
Key words: independent event
What is meant by the term expected ratio?
Reveal answer
Long-run theoretical proportion predicted by a model.
Key words: expected ratio
What is meant by the term observed frequency?
Reveal answer
Number or proportion actually recorded.
Key words: observed frequency
Probability representations, Fraction. Example? Interpretation?
Reveal answer
Example: 1/4. Interpretation: One favourable outcome among four equal combinations.
Key words: Fraction
Probability representations, Decimal. Example? Interpretation?
Reveal answer
Example: 0.25. Interpretation: Probability on a 0–1 scale.
Key words: Decimal
Probability representations, Percentage. Example? Interpretation?
Reveal answer
Example: 25%. Interpretation: Expected proportion per hundred trials.
Key words: Percentage
Probability representations, Ratio. Example? Interpretation?
Reveal answer
Example: 3:1. Interpretation: Relative expected counts of two classes.
Key words: Ratio
Probability representations, Observed frequency. Example? Interpretation?
Reveal answer
Example: Data-dependent. Interpretation: Actual sample outcome.
Key words: Observed frequency
True or false, and why? “After three unaffected children, the fourth must be affected.”
Reveal answer
False. Each fertilisation is an independent event.
True or false, and why? “A Punnett square predicts the exact number in one family.”
Reveal answer
False. It gives theoretical probabilities.
True or false, and why? “25% and 1:3 mean the same ratio notation.”
Reveal answer
False. 25% affected corresponds to affected:unaffected = 1:3.