Gene Control: Regulating how much of a protein gets made Complicated systems usually have parts that control what happens and how fast it happens. Do Now: 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

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.

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?

The lac operon Regulates Gene Expression lac operon structure REPRESSION : OFF INDUCTION : ON No LactoseLactose

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.

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.

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.

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

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

Homework Finish Worksheet if you have not Read “Control of Gene Expression” p.203 – 205. Quiz tomorrow Mutation Files Response Paragraphs (if I don’t have them) Optional – p deal with mRNA processing.

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