A couple has four daughters. What is the correct statement about the chance that the fifth child will be a boy?
Answer and explanation
Correct answer: The chance is again approximately one half.
The governing concept is independent probability in sex determination. In the simplified human XX–XY model, each pregnancy involves a new fertilisation event: an X-bearing or Y-bearing sperm may fertilise the X-bearing egg. Therefore, earlier daughters do not alter the next probability, which is approximately 1/2 for a boy. Option B is correct; options A, C and D incorrectly treat births as predetermined or dependent.
Frequently asked questions
What is the correct answer to this question?
The chance is again approximately one half.
Why is this the correct answer?
The governing concept is independent probability in sex determination. In the simplified human XX–XY model, each pregnancy involves a new fertilisation event: an X-bearing or Y-bearing sperm may fertilise the X-bearing egg. Therefore, earlier daughters do not alter the next probability, which is approximately 1/2 for a boy. Option B is correct; options A, C and D incorrectly treat births as predetermined or dependent.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: World of Living. Topic: Heredity and Evolution.
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