Chapter 18 Genetics of Viruses and Bacteria
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Transcript of Chapter 18 Genetics of Viruses and Bacteria
Chapter 18Genetics 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
Gene RegulationHigh levels of tryptophan inhibits the
first enzyme in the process that makes more tryptophan.
Gene RegulationThis is negative feedback.
Gene RegulationThis is negative feedback.
Making tryptophan
Gene RegulationThis is negative feedback.
means
Making tryptophan we
have
more
Gene RegulationThis is negative feedback.
which inhibits
means
Making tryptophan we
have
more
Gene RegulationThis is negative feedback.
which inhibits
means
Making tryptophan we
have
more
Gene RegulationNegative feedback is also used to regulate the genes that make the
five enzymes that make tryptophan.
A B C D E
Gene RegulationDNA codes for these enzymes.
======================EDCBA=====
Gene RegulationRNA polymerase has to attach to the DNA
to start transcription of the genes.
======================EDCBA=====
Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
Gene RegulationRNA polymerase makes the mRNA for the five enzymes.
======================EDCBA=====
EDCBA
Gene RegulationThe mRNA goes to the ribosomes where the five enzymes are made.
======================EDCBA=====
ABCDE
Gene RegulationThe five enzymes make tryptophan.
======================EDCBA=====
Gene RegulationWhen there is enough tryptophan, the first enzyme is inhibited.
======================EDCBA=====
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
Gene RegulationYou really don’t need all those enzymes if you’re not
using them.
======================EDCBA=====
Gene RegulationYou want to be able to shut off the gene. Actually, you
want to shut off all 5 genes.
======================EDCBA=====
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
Gene RegulationThe repressor is inactive.
==trpR================EDCBA=====
Gene RegulationIt needs tryptophan to be a corepressor in order to activate it.
==trpR================EDCBA=====
Gene RegulationWhen there is a lot of tryptophan, enough repressor is activated to
shut down the gene.
==trpR================EDCBA=====
Gene RegulationThe activated repressor binds to the operator region inside the promoter.
==trpR================EDCBA=====
Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
Gene RegulationThe operon includes the promoter, operator, and all five genes.
==trpR================EDCBA=====
Gene RegulationThe regulatory gene is separate.
==trpR================EDCBA=====
Gene RegulationThe repressor is inactive
==trpR================EDCBA=====
Gene RegulationThe repressor is inactive
until the corepressor binds to it.
==trpR================EDCBA=====
Gene RegulationThe genes that make tryptophan are repressible genes.
==trpR================EDCBA=====
Positive Feedback
Positive FeedbackE. coli needs three separate enzymes to
digest lactose.
Positive FeedbackTryptophan was something the cell
needed to make, so the trp gene was repressed by tryptophan.
Positive FeedbackLactose is something the cell needs to digest, so the lac gene is induced by
lactose.
Positive FeedbackThe lac genes are inducible genes.
=========== lacL ======ZYA========
Positive FeedbackThe regulatory gene, lacL, makes an active repressor.
=========== lacL ======ZYA========
Positive FeedbackThe repressor binds to the operator region within the promoter.
=========== lacL ======ZYA========
=
Positive FeedbackRNA polymerase is blocked from transcribing the structural genes.
=========== lacL ======ZYA========
Positive FeedbackLactose is an inducer.
=========== lacL ======ZYA========
Positive FeedbackIt 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