Getting the Bt toxin expressed: making the mRNA message and the switches that control its production

I. Getting the cry1Ab gene expressed as protein

A. DNA to protein?

B. Overview of how information in DNA is converted into protein

II. Overview of RNA

A. RNA vs DNA

III. Transcription

A. Overview

B. RNA polymerase activity

C. Template strand of DNA

D. Elongation of RNA

IV. Regulation (where does it start and how often does it start) of Transcription

A. Promoters: determines where transcription starts

B. Switches: DNA sequences that turn gene expression on/off (how often transcription happens)

C. Transcription factors: proteins that bind to switches to turn gene expression on/off

D. Using E35S promoter to express Cry1Ab

E. Transcriptional control of cell fate differences (how different cell types are made!)

Study Questions:

1. What is a similarity and a differences between DNA and RNA?

2. What is the function of an RNA polymerase?

3. What is one similarity and one difference between RNA and DNA polymerases?

4. 5’ATGGATTTGTGA3’

Shown above is a single strand of DNA. What would its complementary sequence be (that is present in a DNA double helix)? If the bottom strand (which you just determined) were the template for transcription, what would be the resulting RNA sequence (make sure and specify the 5’ and 3’ ends and substitute U for T)?

5. What is a promoter? What is its major function?

6. What is a switch? What is its major function?

7. If you placed a switch from a highly expressed gene upstream of the promoter of a poorly expressed gene, what would be the effect on transcription of that gene?

8. What is a transcription factor? What is its major function?

9. Would changing the DNA sequence of a switch alter the expression of the gene it regulates? Why?

10. Why were the E35S sequences placed upstream of Cry1Ab in the T DNA plasmid? What would be the effect of removing them on the resulting GMO plant?

11. What makes one cell type different from another cell type? (the DNA in the cells, the genes present in the cells, the presence of RNA polymerase in the cells, the switches in the DNA in the cells, or the transcription factors in the cells)

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