Campbell Biology (10th Edition)

Published by Pearson
ISBN 10: 0321775651
ISBN 13: 978-0-32177-565-8

Chapter 13 - Test Your Understanding - Level 3 - Synthesis/Evaluation: 9

Answer

The crossing over shown in question 6 shows one crossing over event between two non-sister chromatids. Thus, the gametes would be two unchanged from the parental types (freckles-black hair; no freckles-blond hair) plus two recombined versions (freckles-blond hair; no freckles-black hair). These are all of the four possible combinations for these two genes with two alleles per gene.

Work Step by Step

Look closely at the diagram in question 6: you can see that two non-sisters from the long chromosome have crossed over while the other two non-sisters have not. This will lead to the described four combinations in the four gametes resulting from this meiosis.
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