Life: The Science of Biology
11th Edition
ISBN: 9781319010164
Author: David E. Sadava, David M. Hillis, H. Craig Heller, Sally D. Hacker
Publisher: W. H. Freeman
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Chapter 23.2, Problem 1R
Summary Introduction
To review:
The mechanism to analyze whether the opsin gene in eyeless crayfish was inherited from an eyed ancestor and then lost its function or it has a new function other than vision.
Introduction:
Crayfish species that live as surface dwellers have functional eyes, while those that live in underground caves have lost their vision. However, both the species show expression of the opsin gene, which plays an important role in vision.
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Opsin proteins detect light in photoreceptor cells of theeye and are required for color vision. The nocturnal owlmonkey, the nocturnal bush baby, and the subterraneanblind mole rat have different mutations in an opsin genethat render it nonfunctional. Explain why all three species can tolerate mutations in this gene that operates inmost other mammals.
We have spent a lot of time comparing channelrhodopsin (which is found in Chlamydomonas) with rhodopsin (which is found in humans).
What about these two photoreceptors is correct?
A. The opsin proteins are homologous and serve as ion channels that transport Ca2+ ions.
B. The opsin proteins aren’t homologous, but both species have homologous enzymes involved in retinal synthesis.
C. The opsin proteins aren’t homologous, but they both interact with G proteins, that do share a common ancestry.
D. The opsin proteins are homologous, they just fold into very different native conformations.
How many globin genes are present in mammals? What is the evidence indicating that all the globin genes in the mammalian genome are part of a family derived from a common ancestral globin gene?
Chapter 23 Solutions
Life: The Science of Biology
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