Introduction to Genetic Analysis 521

Introduction to Genetic Analysis 521 - Case B Case C Case D...

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520 Chapter 15 Large-Scale Chromosomal Changes a. Provide reasonable explanations for these three exceptional octads. b. Diagram the meiosis that gave rise to octad 2. 55. The life cycle of the haploid fungus Ascobolus is sim- ilar to that of Neurospora. A mutational treatment produced two mutant strains, 1 and 2, both of which when crossed to wild type gave unordered tetrads, all of the following type (fawn is a light-brown color; normally, crosses produce all black ascospores): spore pair 1 black spore pair 2 black spore pair 3 fawn spore pair 4 fawn a. What does this result show? Explain. The two mutant strains were crossed. Most of the unordered tetrads were of the following type: spore pair 1 fawn spore pair 2 fawn spore pair 3 fawn spore pair 4 fawn Case A
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Unformatted text preview: Case B Case C Case D spore pair 1 black black black black spore pair 2 black fawn black abort spore pair 3 fawn fawn abort fawn spore pair 4 fawn fawn abort fawn b. What does this result suggest? Explain. When large numbers of unordered tetrads were screened under the microscope, some rare ones that contained black spores were found. Four cases are shown here: ( Note: Ascospores with extra genetic material sur-vive, but those with less than a haploid genome abort.) c. Propose reasonable genetic explanations for each of these four rare cases. d. Do you think the mutations in the two original mutant strains were in one single gene? Explain. 44200_15_p481-520 3/12/04 1:07 PM Page 520...
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