Concepts of Genetics Plus Mastering Genetics with Pearson eText -- Access Card Package (12th Edition) (What's New in Genetics)
12th Edition
ISBN: 9780134811390
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Textbook Question
Chapter 25, Problem 29ESP
In 1988, Horst Wilkens investigated blind cavefish, comparing them with members of a sibling species with normal vision that are found in a lake [Wilkens, H. (1988). Evol. Biol. 25:271–367]. We will call them cavefish and lakefish. Wilkens found that cavefish eyes are about seven times smaller than lakefish eyes. F1 hybrids have eyes of intermediate size. These data, as well as the F1 × F1 cross and those from backcrosses (F1 × cavefish and F1 × lakefish), are depicted below. Examine Wilkens’s results and respond to the following questions:
- (a) Based strictly on the F1 and F2 results of Wilkens’s initial crosses, what possible explanation concerning the inheritance of eye size seems most feasible?
- (b) Based on the results of the F1 backcross with cavefish, is your explanation supported? Explain.
- (c) Based on the results of the F1 backcross with lakefish, is your explanation supported? Explain.
- (d) Wilkens examined about 1000 F2 progeny and estimated that 6–7 genes are involved in determining eye size. Is the
sample size adequate to justify this conclusion? Propose an experimental protocol to test the hypothesis. - (e) A comparison of the embryonic eye in cavefish and lakefish revealed that both reach approximately 4 mm in diameter. However, lakefish eyes continue to grow, while cavefish eye size is greatly reduced. Speculate on the role of the genes involved in this problem.
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Chapter 25 Solutions
Concepts of Genetics Plus Mastering Genetics with Pearson eText -- Access Card Package (12th Edition) (What's New in Genetics)
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