HORT 250 Mid-Term Exam 1999
1. As the genetic material, DNA must be able to perform three functions:
How does DNA perform each of these functions? (12 points)
2. The diagram below shows the structure of a typical gene that encodes a protein. Label the arrows that point to the essential components that are required for transcription of this gene into RNA and subsequent translation into protein. (14 points)
3. Provide a one sentence definition of each of the following: (2 points each)
4. Describe how expression of the beta-galactosidase gene in E. coli is repressed (switched off) when lactose is not available in the medium, and induced (switched on) when lactose is present. (10 points)
Describe one similarity and one difference between prokaryotes and eukaryotes in how they regulate gene expression. (4 points)
5. You have just isolated a gene encoding a protein that makes pigs grow more quickly. In order to make enough of this protein to treat all the pigs in Indiana (that's a lot of pigs), you will have to produce this protein in bacteria. Draw and label a diagram showing the essential features of the protein expression vector (plasmid) that you will use to make this protein in bacteria. (10 points)
6. Why are selectable marker genes used in virtually all transformation experiments? (6 points)
Why will a bacterial gene for kanamycin resistance not be expressed in plants? (2 points)
Outline the modifications that must be made to this bacterial gene before it can be used as a selectable marker in plants. (4 points)
7. Agrobacterium tumefaciens is both a pathogen and an invaluable tool for transformation of plants. Briefly describe how this bacterium causes crown gall disease (tumors) on plants. (6 points)
When Agrobacterium tumefaciens is used for transformation of plants, what modifications are made to the T-DNA in the Ti plasmid? (4 points)
Outline a typical plant transformation procedure using Agrobacterium tumefaciens as the vector to deliver DNA. (10 points)
Describe one of the physical methods that are used to deliver DNA into plant cells. (4 points)
8. Describe two similarities between the herbicides glyphosate (Roundup) and glufosinate (Liberty). (4 points)
Genes have been isolated from bacteria and transferred into plants to develop crops with resistance to these herbicides.
What are the biochemical properties of the EPSP synthase from Agrobacterium that has been used to make plants resistant to glyphosate? (4 points)
What does the enzyme from Streptomyces do to make plants resistant to glufosinate? (4 points)
What are the two sources of income that Monsanto now receives as a result of developing Roundup Ready soybeans? (4 points)
What impact has RoundUp Ready soybeans had on the sales and prices of individual herbicides used for weed control in soybeans? (4 points)
What is likely to happen to weed populations if growers repeatedly apply RoundUp to the same fields year after year? (4 points)
BONUS QUESTION
9. The Goldsbrough Mega Corporation (ticker symbol GMC on the NYSE) has discovered a new herbicide, "Gold", that kills all plants. Following the successful business model of Monsanto and Roundup, they want to develop crop plants that are resistant to this herbicide. However, they want to avoid using gene transfer methods so that these crops will be classified as traditional varieties and not GMOs. Describe how they might proceed to develop "Gold"-resistant corn and make CEO Goldsbrough stunningly wealthy. (6 points)