Lesson: Chapter 20 — Heredity

20.6. Genetic disorders 7 of 8 Reset answers

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Question 7

How many chromosomes are there in the body cells of a person with Down syndrome?

A 48 B 47 C 45 D 46

The right answer is the one marked above.

47. There are three copies of chromosome 21 instead of two, so the total is one more than the usual 46.

This arises when a homologous pair fails to separate during meiosis, so one gamete receives both chromosomes of the pair.

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