HORT 250 Final Exam 1999

1. Provide a brief description of each of the following elements of a gene: (2 pts each, 14 pts)

a) Promoter

b) Transcription start site

c) ATG codon

d) Open reading frame

e) Repressor binding site

f) Ribosome binding site

g) Intron

2. Agrobacterium tumefaciens is widely used to produce transgenic plants. Draw a labeled diagram showing the essential features of a typical modified Ti plasmid used for plant tranformation. (7 pts)

Outline the procedure used to produce transgenic plants using microprojectile bombardment. (7 pts)

3. Plants with improved insect resistance have been produced by expressing Bt toxins in transgenic plants. You are provided with a gene encoding a Bt protoxin cloned from a bacterium. Starting with this gene, describe what you would do to produce a chimeric gene that will direct the expression of the mature Bt toxin only in leaves and stalks of transgenic corn plants. (Do not describe how to produce transgenic corn plants.) (7 pts)

Compared to conventional insecticides, what are the advantages of using plants expressing insecticidal proteins such as Bt toxin to control insect damage? (7 pts)

4. Describe the procedures that growers of Bt crops are required to use to slow down the development of insect populations with resistance to Bt toxins. (3 pts)

Describe the scientific basis for behind these procedures. (4 pts)

What alternatives are there to Bt toxins for producing plants with insect resistance? (4 pts)

What can be done to make transgenic plants to which insects are less likely to become resistant? (3 pts)

5. How does ethylene control the ripening of tomato fruits? (2 pts)

Describe three methods that have been used to reduce the synthesis of ethylene, and slow down fruit ripening, in tomato. (9 pts)

What approaches have been used to increase the soluble solids content of processing tomatoes? (3 pts)

6. The papaya industry in Hawaii has suffered from losses caused by papaya ringspot virus. How have transgenic papaya plants been produced that are resistant to this virus? (7 pts)

How is this method of protection thought to function? (3 pts)

Briefly describe another method that has been used to produce plants that are resistant to a virus. (4 pts)

7. Describe one approach that has been used to make plants more tolerant of an environmental condition by producing more of a specific metabolite (compound). (5 pts)

Describe an alternative approach used to make plants more resistant to low temperatures by expressing a regulatory factor. (5 pts)

You are an activist at an environmental group. What potential problem(s) do you see with crop plants that are engineered to grow better in harsh environments? (4 pts)

8. A biotech company has developed transgenic sunflowers that carry a gene for resistance to a soil nematode. What questions will the three agencies that regulate ag biotech products (USDA, EPA, FDA) have about these plants? (14 pts) (You might want to check out the following web site for this topic: http://ificinfo.health.org/brochure/bioregs.htm)

9. I have just discovered a promoter that gives very high expression in developing flower petals. What criteria must be met and what do I have to do to file for a patent on the use of this promoter? (7 pts)

Once the patent has been issued, describe 3 approaches I can take in order to make enough money from this discovery to pay for my daughter's braces (or any other medical procedure). (7 pts)

10. Describe how transgenic animals are produced by microinjection of fertilized eggs. (7 pts)

How can transgenic animals be used to produce valuable therapeutic proteins, such as clotting factors, that can be used to treat human diseases? (7 pts)