Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.

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Presentation transcript:

Chapter 18 Genetics of Viruses and Bacteria Gene Regulation

Your body needs to make tryptophan. Gene Regulation

There are 5 steps to making tryptophan. Gene Regulation

Eventually you have enough tryptophan. Gene Regulation

High levels of tryptophan inhibits the first enzyme in the process that makes more tryptophan.

Gene Regulation This is negative feedback.

Gene Regulation This is negative feedback. Making tryptophan

Gene Regulation This is negative feedback. means Making tryptophan we have more

Gene Regulation This is negative feedback. which inhibits means Making tryptophan we have more

Gene Regulation This is negative feedback. which inhibits means Making tryptophan we have more

Gene Regulation Negative feedback is also used to regulate the genes that make the five enzymes that make tryptophan. A B C D E

Gene Regulation DNA codes for these enzymes. ======================EDCBA=====

Gene Regulation RNA polymerase has to attach to the DNA to start transcription of the genes. ======================EDCBA=====

Gene Regulation It needs a place to attach. The promoter is a region of DNA that marks the beginning of the gene. ======================EDCBA=====

Gene Regulation It needs a place to attach. The promoter is a region of DNA that marks the beginning of the gene. ======================EDCBA=====

Gene Regulation It needs a place to attach. The promoter is a region of DNA that marks the beginning of the gene. ======================EDCBA=====

Gene Regulation RNA polymerase makes the mRNA for the five enzymes. ======================EDCBA===== EDCBA

Gene Regulation The mRNA goes to the ribosomes where the five enzymes are made. ======================EDCBA===== ABCDE

Gene Regulation The five enzymes make tryptophan. ======================EDCBA=====

Gene Regulation When there is enough tryptophan, the first enzyme is inhibited. ======================EDCBA=====

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA=====

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA===== ABCDE

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA===== ABCDE

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA=====

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA===== ABCDE

Gene Regulation But the genes could still go on making more enzymes. ======================EDCBA===== ABCDE

Gene Regulation You really don’t need all those enzymes if you’re not using them. ======================EDCBA=====

Gene Regulation You want to be able to shut off the gene. Actually, you want to shut off all 5 genes. ======================EDCBA=====

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA=====

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA=====

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA=====

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA===== trpR

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA===== trpR

Gene Regulation The repressor gene trpR makes a repressor molecule. ==trpR================EDCBA===== trpR

Gene Regulation The repressor is inactive. ==trpR================EDCBA=====

Gene Regulation It needs tryptophan to be a corepressor in order to activate it. ==trpR================EDCBA=====

Gene Regulation When there is a lot of tryptophan, enough repressor is activated to shut down the gene. ==trpR================EDCBA=====

Gene Regulation The activated repressor binds to the operator region inside the promoter. ==trpR================EDCBA=====

Gene Regulation This prevents RNA polymerase from binding to DNA. ==trpR================EDCBA=====

Gene Regulation This prevents RNA polymerase from binding to DNA. ==trpR================EDCBA=====

Gene Regulation This prevents RNA polymerase from binding to DNA. ==trpR================EDCBA=====

Gene Regulation The operon includes the promoter, operator, and all five genes. ==trpR================EDCBA=====

Gene Regulation The regulatory gene is separate. ==trpR================EDCBA=====

Gene Regulation The repressor is inactive ==trpR================EDCBA=====

Gene Regulation The repressor is inactive until the corepressor binds to it. ==trpR================EDCBA=====

Gene Regulation The genes that make tryptophan are repressible genes. ==trpR================EDCBA=====

Positive Feedback

E. coli needs three separate enzymes to digest lactose.

Positive Feedback Tryptophan was something the cell needed to make, so the trp gene was repressed by tryptophan.

Positive Feedback Lactose is something the cell needs to digest, so the lac gene is induced by lactose.

Positive Feedback The lac genes are inducible genes. =========== lacL ======ZYA========

Positive Feedback The regulatory gene, lacL, makes an active repressor. =========== lacL ======ZYA========

Positive Feedback The repressor binds to the operator region within the promoter. =========== lacL ======ZYA======== =

Positive Feedback RNA polymerase is blocked from transcribing the structural genes. =========== lacL ======ZYA========

Positive Feedback Lactose is an inducer. =========== lacL ======ZYA========

Positive Feedback It inactivates the repressor. =========== lacL ======ZYA========

It inactivates the repressor. =========== lacL ======ZYA======== Positive Feedback

It inactivates the repressor. =========== lacL ======ZYA======== ZYA Positive Feedback

It inactivates the repressor. =========== lacL ======ZYA======== ZYA Positive Feedback

It inactivates the repressor. =========== lacL ======ZYA======== usable energy Positive Feedback

But there’s more… =========== lacL ======ZYA======== Positive Feedback

But there’s more… If glucose is available, the cell would rather use that than lactose =========== lacL ======ZYA======== Positive Feedback

If there is a shortage of glucose, the cell builds up quantities of cAMP. =========== lacL ======ZYA======== Positive Feedback

cAMP is a cofactor for another regulatory protein called CRP. (cAMP receptor protein) =========== lacL ======ZYA======== Positive Feedback

cAMP activates CRP. =========== lacL ======ZYA======== Positive Feedback

CRP makes the lac genes much more active. =========== lacL ======ZYA======== Positive Feedback

So less glucose means more lactose gets digested. =========== lacL ======ZYA======== Positive Feedback

More glucose means you don’t need to digest the lactose even if it’s there… =========== lacL ======ZYA======== Positive Feedback

More glucose means very little cAMP. =========== lacL ======ZYA======== Positive Feedback

Without cAMP, CRP is inactive. =========== lacL ======ZYA======== Positive Feedback

Without CRP, the lac genes are less active. =========== lacL ======ZYA======== Positive Feedback

Without cAMP, CRP is inactive. =========== lacL ======ZYA======== Positive Feedback