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Question 64

A student reads the ratio 3 to 1 predicted for a monohybrid cross as a 3 in 1 chance of showing the dominant characteristic. How should that ratio be read instead?

  1. It means 3 out of every 3 offspring, so every offspring shows it
  2. It means 3 out of every 4 offspring, which is a chance of 75 per centCorrect answer
  3. It means 1 out of every 3 offspring, a chance of about 33 per cent
  4. It means the dominant characteristic appears three generations later

Explanation

The parts of a ratio are added to find the total, so 3 to 1 describes four offspring in all, three of one kind and one of the other, and the chance for each offspring is three out of those four. A 3 in 1 chance is not a chance at all, since a chance cannot exceed one; the 3 and the 1 are parts of a total of four. Reading the prediction instead as 3 out of 3 quietly drops the fourth part and turns a statement about most offspring into a claim about all of them.

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Question 64: A student reads the ratio 3 to 1 predicted for a monohybrid… · Genetics Basics · Questena