N Chapter 18~ Microbial Models: The Genetics of Viruses and Bacteria.
Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.
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Transcript of Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.
![Page 1: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/1.jpg)
Chapter 18Genetics of Viruses and Bacteria
Gene Regulation
![Page 2: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/2.jpg)
Your body needs to make tryptophan.
Gene Regulation
![Page 3: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/3.jpg)
There are 5 steps to making tryptophan.
Gene Regulation
![Page 4: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/4.jpg)
Eventually you have enough tryptophan.
Gene Regulation
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Gene RegulationHigh levels of tryptophan inhibits the
first enzyme in the process that makes more tryptophan.
![Page 6: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/6.jpg)
Gene RegulationThis is negative feedback.
![Page 7: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/7.jpg)
Gene RegulationThis is negative feedback.
Making tryptophan
![Page 8: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/8.jpg)
Gene RegulationThis is negative feedback.
means
Making tryptophan we
have
more
![Page 9: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/9.jpg)
Gene RegulationThis is negative feedback.
which inhibits
means
Making tryptophan we
have
more
![Page 10: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/10.jpg)
Gene RegulationThis is negative feedback.
which inhibits
means
Making tryptophan we
have
more
![Page 11: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/11.jpg)
Gene RegulationNegative feedback is also used to regulate the genes that make the
five enzymes that make tryptophan.
A B C D E
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Gene RegulationDNA codes for these enzymes.
======================EDCBA=====
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Gene RegulationRNA polymerase has to attach to the DNA
to start transcription of the genes.
======================EDCBA=====
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Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
![Page 15: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/15.jpg)
Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
![Page 16: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/16.jpg)
Gene RegulationIt needs a place to attach.
The promoter is a region of DNA that marks the beginning of the gene.
======================EDCBA=====
![Page 17: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/17.jpg)
Gene RegulationRNA polymerase makes the mRNA for the five enzymes.
======================EDCBA=====
EDCBA
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Gene RegulationThe mRNA goes to the ribosomes where the five enzymes are made.
======================EDCBA=====
ABCDE
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Gene RegulationThe five enzymes make tryptophan.
======================EDCBA=====
![Page 20: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/20.jpg)
Gene RegulationWhen there is enough tryptophan, the first enzyme is inhibited.
======================EDCBA=====
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Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
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Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
![Page 23: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/23.jpg)
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
![Page 24: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/24.jpg)
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
![Page 25: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/25.jpg)
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
![Page 26: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/26.jpg)
Gene RegulationBut the genes could still go on making more enzymes.
======================EDCBA=====
ABCDE
![Page 27: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/27.jpg)
Gene RegulationYou really don’t need all those enzymes if you’re not
using them.
======================EDCBA=====
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Gene RegulationYou want to be able to shut off the gene. Actually, you
want to shut off all 5 genes.
======================EDCBA=====
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Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
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Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
![Page 31: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/31.jpg)
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
![Page 32: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/32.jpg)
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
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Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
![Page 34: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/34.jpg)
Gene RegulationThe repressor gene trpR makes a repressor molecule.
==trpR================EDCBA=====
trpR
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Gene RegulationThe repressor is inactive.
==trpR================EDCBA=====
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Gene RegulationIt needs tryptophan to be a corepressor in order to activate it.
==trpR================EDCBA=====
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Gene RegulationWhen there is a lot of tryptophan, enough repressor is activated to
shut down the gene.
==trpR================EDCBA=====
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Gene RegulationThe activated repressor binds to the operator region inside the promoter.
==trpR================EDCBA=====
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Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
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Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
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Gene RegulationThis prevents RNA polymerase from binding to DNA.
==trpR================EDCBA=====
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Gene RegulationThe operon includes the promoter, operator, and all five genes.
==trpR================EDCBA=====
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Gene RegulationThe regulatory gene is separate.
==trpR================EDCBA=====
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Gene RegulationThe repressor is inactive
==trpR================EDCBA=====
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Gene RegulationThe repressor is inactive
until the corepressor binds to it.
==trpR================EDCBA=====
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Gene RegulationThe genes that make tryptophan are repressible genes.
==trpR================EDCBA=====
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Positive Feedback
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Positive FeedbackE. coli needs three separate enzymes to
digest lactose.
![Page 49: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/49.jpg)
Positive FeedbackTryptophan was something the cell
needed to make, so the trp gene was repressed by tryptophan.
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Positive FeedbackLactose is something the cell needs to digest, so the lac gene is induced by
lactose.
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Positive FeedbackThe lac genes are inducible genes.
=========== lacL ======ZYA========
![Page 52: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/52.jpg)
Positive FeedbackThe regulatory gene, lacL, makes an active repressor.
=========== lacL ======ZYA========
![Page 53: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/53.jpg)
Positive FeedbackThe repressor binds to the operator region within the promoter.
=========== lacL ======ZYA========
=
![Page 54: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/54.jpg)
Positive FeedbackRNA polymerase is blocked from transcribing the structural genes.
=========== lacL ======ZYA========
![Page 55: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/55.jpg)
Positive FeedbackLactose is an inducer.
=========== lacL ======ZYA========
![Page 56: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/56.jpg)
Positive FeedbackIt inactivates the repressor.
=========== lacL ======ZYA========
![Page 57: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/57.jpg)
It inactivates the repressor.
=========== lacL ======ZYA========
Positive Feedback
![Page 58: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/58.jpg)
It inactivates the repressor.
=========== lacL ======ZYA========
ZYA
Positive Feedback
![Page 59: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/59.jpg)
It inactivates the repressor.
=========== lacL ======ZYA========
ZYA
Positive Feedback
![Page 60: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/60.jpg)
It inactivates the repressor.
=========== lacL ======ZYA========
usable energy
Positive Feedback
![Page 61: Chapter 18 Genetics of Viruses and Bacteria Gene Regulation.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649d195503460f949ee885/html5/thumbnails/61.jpg)
But there’s more…
=========== lacL ======ZYA========
Positive Feedback
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But there’s more…
If glucose is available, the cell would rather use that than lactose
=========== lacL ======ZYA========
Positive Feedback
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If there is a shortage of glucose, the cell builds up quantities of cAMP.
=========== lacL ======ZYA========
Positive Feedback
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cAMP is a cofactor for another regulatory protein called CRP.
(cAMP receptor protein)
=========== lacL ======ZYA========
Positive Feedback
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cAMP activates CRP.
=========== lacL ======ZYA========
Positive Feedback
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CRP makes the lac genes much more active.
=========== lacL ======ZYA========
Positive Feedback
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So less glucose means more lactose gets digested.
=========== lacL ======ZYA========
Positive Feedback
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More glucose means you don’t need to digest the lactose even if it’s there…
=========== lacL ======ZYA========
Positive Feedback
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More glucose means very little cAMP.
=========== lacL ======ZYA========
Positive Feedback
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Without cAMP, CRP is inactive.
=========== lacL ======ZYA========
Positive Feedback
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Without CRP, the lac genes are less active.
=========== lacL ======ZYA========
Positive Feedback
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Without cAMP, CRP is inactive.
=========== lacL ======ZYA========
Positive Feedback