BT 210

Lecture Outline- Week 8

Return to Lecture Table of Contents

Control of Procaryotic Gene Expression

At this point in the semester, we've already talked about genes at some length. We've talked about how to locate a "gene of interest" on a chromosome, and having done so, how to make more of it. But what is a gene really? We know that it is composed of DNA, but what else do we know? This will be our lecture topic for this week. Today we will discuss gene structure and function in procaryotes (i.e. bacteria), and next time we will discuss gene structure and function in eucaryotes.

I. Structurally, What Makes Up a Gene?

A. Coding sequences

-- central dogma review

-- what do coding sequences do?

B. A gene is more than just a coding sequence...

-- cells must have a way of controlling expression of individual genes

-- in procaryotes, most gene expression is controlled at the level of

transcription

-- the lifestyle of the procaryotic cell

II. How are Genes Organized on the Bacterial Chromosome?

A. The genes are structured and the genome organized to meet the expression control needs of the procaryotic cell

-- most bacterial genes are arranged into operons

B. Operon structure

-- protein coding region

-- signals for mRNA synthesis

-- upstream regulatory elements

C. Examples of operons

-- the lac operon

-- the arabinose operon

The control region of the E. coli arabinose operon has been cloned upstream of the GFP gene in pGLO, the plasmid used in Protocol #6. Therefore, the same conditions that drive expression from the arabinose operon in the E. coli chromosome, will drive expression of the GFP gene in the pGLO plasmid.