PLB 113 Homework_3_Key_Spring_2009

PLB 113 Homework_3_Key_Spring_2009 - PLANT BIOLOGY 113...

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PLANT BIOLOGY 113 Spring 2009 Instructor: Professor S. O’Neill 1 HOMEWORK QUESTIONS #3 KEY (50 points) 1. You have isolated a dwarf mutant, designated dwf1 , that is smaller in stature than a wild type plant. You have isolated the wild type DWF1 gene and proven that this gene corresponds to the mutation in dwf1 . To learn more about the function of the gene, you transfer the wild type DWF1 gene into wild type plants and obtain many independent transformants. You measure the final heights of each transformant as well as the wild type and dwf1 mutant, and obtain the following results. Discuss possible reasons to explain why the transgenic plants containing the DWF1 vary in stature. Describe an experiment to test your idea. Possible reasons for the range of transformant plant heights: A mutation in the DWF1 gene results in a dwarf phenotype. This result suggests that the wild type DWF1 gene functions to increase plant height. Transformants #2, 4, and 6 are taller than wild type plants. One interpretation is that expression of the DWF1 transgene causes overaccumulation of the DWF1 gene product and, therefore, an increase in height. These transformants may reach different heights because the transgene may be expressed at different levels in each of these transformants. Transformant #1 is the same height as wild type plants. This result may indicate that the transgene is not active in this plant. Transformants #3 and 5 are smaller than wild type. In these plants, the transgene may cause co-suppression of the endogenous gene to varying extents. These hypotheses could be tested by measuring DWF1 protein or mRNA levels in each transformant. If these ideas are correct, one would expect DWF1 protein or mRNA levels to be: Higher than wild type in transformants #2,4, and 6 Equivalent to wild type levels in transformant #1 Lower than wild type in transformants #3 and 5.
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PLANT BIOLOGY 113 Spring 2009 Instructor: Professor S. O’Neill 2 2. You have constructed a Ti plasmid with the modified T-DNA region shown below. DNA fragments containing individual components of a wild type T-DNA have been
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This note was uploaded on 12/13/2009 for the course PLB 113 taught by Professor O'neil during the Spring '09 term at UC Davis.

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PLB 113 Homework_3_Key_Spring_2009 - PLANT BIOLOGY 113...

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