Bsc 2010 Lesson 23

Front 1

virus

Back 1

aninfectious particle consisting of genes packaged in a protein coat

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Plasmids, transposons, and viruses

Back 2

mobilegenetic elements (3)

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tobacco mosaic disease

Back 3

stuntsgrowth of tobacco plants and gives their leaves a mosaic coloration

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Adolf Mayer

Back 4

discoveredthat he could transmit the disease by rubbing sap extracted from one diseasedleaf to a healthy plant

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Dimitri Ivanowsky

Back 5

passed the sap through a filterdesigned to remove bacteria.

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Martinus Beijerinck

Back 6

Hereasoned that the agent was smaller and simpler than bacteria and is creditedwith the concept of a virus

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wendell Stanley

Back 7

confirmedthis hypothesis by crystallizing the infectious particle, now known as tobaccomosaic virus (TMV)

Front 8

-Nucleic acid

-Capsid

-capsomeres

-membranous envelope

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A virus is a very small infectiousparticle consisting of

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viral envelopes

Back 9

(derivedfrom membranes of host cells) surround the capsids of influenza viruses andmany other viruses found in animals

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bacteriophages

Back 10

viruses that infect bacteria

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host range

Back 11

alimited number of host cells that it can infect

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lytic cycle

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aphage replicative cycle that culminates in the death of the host cell

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virulent phage

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A phage that reproduces only by thelytic cycle

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restriction enzymes

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Bacteria defense against phages that recognize and cut up certainphage DNA

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lysogenic cycle

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§replicatesthe phage genome without destroying the host

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prophage

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integrated viral DNA

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temperate phages

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Phages that use both the lytic andlysogenic cycles

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parvovirus

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ex. of single-stranded DNA virus

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herpes

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ex. of double-stranded DNA virus

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rhinovirus

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ex. of single-stranded RNA virus

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rotavirus

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ex. of double-stranded RNA virus

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retroviruses

ex. HIV produces AIDS

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use reversetranscriptase tocopy their RNA genome into DNA

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provirus

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The viral DNA that is integratedinto the host genome and does not leave the host cell

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mutations

Back 24

creates adaptive changes inproteins

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genetic recombinations

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transfers DNA from one bacteriumto another

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transformation

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bacterial cell takes up DNA from dead cells outside and combines it with itsown DNA

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transduction

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infecting bacterial virus (phage)introduces DNA from previous hosts

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conjunction

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transfer of specific plasmids from onebacterium to another

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rearrangement of transposons

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affects overall gene expression

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feedback inhibition or gene regulation

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A cell can regulate the productionof enzymes by

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operon model

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One mechanism for control of geneexpression in bacteria is (Discovered by Francois Jaciband Jacques Monod in 1961)

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operator

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Acluster of functionally related genes can be coordinately controlled by asingle “on-offswitch” called

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operon

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theentire stretch of DNA that includes the operator, the promoter, and the genesthat they control

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repressor

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The operon can be switched off by aprotein ______.

-preventsgene transcription by binding to the operator and blocking RNA polymerase

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corepressor

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§amolecule that cooperates with a repressor protein to switch an operon off

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repressible operon

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operon thatis usually on; binding of a repressor to theoperator shuts off transcription (trp)

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inducible operon

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operon that is usuallyoff;a molecule called an inducer inactivates the repressor and turns ontranscription (lac)

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inducer

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inactivatesthe repressor to turn the lacoperon on

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catabolic pathways

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Inducibleenzymes usually function in _______ _________; their synthesis is induced byachemical signal

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anabolic pathways

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Repressibleenzymes usually function in _________ __________; their synthesis is repressed byhigh levels of the end product