1. 3.13: Gene Control: Regulating protein production (HW check 10.15-16!)
Objectives: 1. define operon, promoter, repression, repressor, induction, and inducer.
2. explain how the presence of an inducer turns on the transcription of lac genes in E. coli.
TASK:
2. What might happen to a cell if it produced lots of protein that it didn’t need? Why might overproduction be a problem?
Waste of ENERGY & Amino Acids

2. System Controls
Each of these “faders” controls the volume of one audio track.
Some can be programmed to move up and down as the song changes from part to part.
The different colors of each square represent the “volume” of one gene.
As a cell grows, matures, and changes, it produces proteins at different rates.

3. The lac Operon By E. coli
The problem:
Lactose is a type of sugar (found in milk) that can be metabolized for energy, just like glucose.
Only cells that produce the lactase enzyme can utilize lactose as a source of energy.
If there’s no lactose around, making the proteins needed to transport lactose and break it down is a BIG waste of resources.
Did You Know???
Over 95% of Native American Indians and Asia-Pacific Islanders cannot digest lactose
Over 95% of Northern European populations can.
Which civilization hunted meat? Which one raised goats and cows?

4. Operons
An operon is a gene plus the control mechanisms associated with it.
Genes begin with a promoter, which is where RNA polymerase attaches to begin transcription.
Many operons include an operator, which controls whether a gene will be repressed (off) or induced (on)

5. The lac operon Regulates Gene Expression
lac operon structure
INDUCTION : ON
REPRESSION : OFF
No Lactose
Lactose

6. lac Operon diagrams
Color each part of the system the same color every place it appears.
If you finish before we move on, begin working on the worksheet on the back.

7. Lac Operon Animations
Lacfinal_redone2.avi
LacOperon QT
As you watch, compare what you see in the two different animations – Hint: check out the repressor protein.

8. Lac operon: The Big Ideas
The ability to control gene expression is vital to living cells. Without it, cells could not adapt to any changes in their environment.
Proteins, DNA, and RNA molecules interact with each other to control gene expression. The lac operon is one example of such a control system
Repressed genes are not expressed, induced / activated genes are expressed.

9. Splicing (mRNA processing)
mRNA splicing does not occur regularly in prokaryotes. Just one more reason they’re easier to work with!
After transcription in eukaryotes, most mRNA molecules get processed before they can be used to direct protein synthesis

10. mRNA Splicing
During this process, introns are removed, and exons are joined together.
If parts of the sequence are combined in different ways, one gene can actually produce several different proteins
It’s a complex process

11. Homework Finish Worksheet if you have not
Reading on syllabus is suggested.
Papers due tomorrow!
Hard copy preferred
by 3:05. If ing, submit prewriting & rubric in class.

12. Closing Thought
Genes are controlled by the complex interactions of DNA, RNA, and proteins.