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SS DNA Virusinfecting host cell

Host DNA dependent DNApolymerase use ssDNA tosynthesize complementarystrand. The original ssDNAstrand may be self priming(with a hairpin structure atone end) or a primer molecule can be brought infrom the capsid. Theresulting dsDNA will then beused as template for mRNAand DNA synthesis usinghost coded DNA Dependentpolymerase enzymes

Host DNA dependentDNA Polymerase

Host DNA dependentRNA polymerase

Viralparticle

CLASS II Viruses ± ssDNA

Host DNA

Viral ssDNA injectedinto cell- used astemplate by host DNA

polymerase tosynthesize dsDNA.

SynthesizeddsDNA. Thisserves astemplate for both mRNAand further

DNAsynthesis.

mRNA (plus ss RNA). mRNA willbe translated to viral proteinsincluding viral enzymes andcapsid

Progeny viral ssDNAresulting fromdegradation of one strandof dsDNA by viralnuclease enzyme

dsDNA

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dsRNA Virusinfecting host cell

V iral RNA dependent RNApolymerase synthesizes (+)ssRNA which is mRNA thatis translated to viral codedproteins. Progeny dsRNA isalso synthesized by RNAdependent RNA polymerase.

Viralparticle

CLASS III Viruses ± dsRNA

Host DNA

(+) ssRNA (mRNA). This stand will be synthesized by the viral RNA dependent RNA polymerase using the minus (-) strand as template.This newly synthesized strand will serve as mRNA and will be translated to viral proteins including viral enzymes that will allow theinfection process to continue. [Note that dsRNA cannot serve as mRNA,. Hence viral RNA dependent RNA polymerase cannot besynthesized directly from the injected dsRNA and must be brought in the capsid. ssRNA (+) is first synthesized and then be translated to

proteins including RNA dependent RNA polymerases and other enzymes/structural components required by the virus.

RNAdependentRNApolymerase

Viral dsRNA

dsRNA(Progenynucleic acid

that will beassembledwith thecapsid.)

tra

nslation

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(+) ssRNA Virusinfecting host cell

(+) ssRNA is first translatedto produce viral codedproteins including RNAdependent RNA polymerase.This enzyme can then beused to synthesize more (+)strands which will serve asboth mRNA and progenyvirus.

Viralparticle

CLASS IV Viruses ± (+) ssRNA

Host DNA

Viral (+)ssRNA.Functionsas mRNA

Synthesized(-) ssRNA translation

(+) ssRNAsynthesized by viralcoded RNAdependent RNApolymerase using (-)strand as template.This can serve asboth mRNA andprogeny virus

Viral coded RNA dependent RNA polymerase synthesizedin host cell since the introduced (+) ssRNA can servedirectly as mRNA

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(-) ssRNA Virusinfecting host cell

(-) ssRNA is transcribed to(+) ssRNA by polymerasebrought by the virus. (+)ssRNA serves as mRNA andalso serves as the templatefor the synthesis of progenyviral nucleic acid (-) ssRNA.

Viralparticle

CLASS V Viruses ± (-)ss RNA

Host DNA

(+) ssRNA (mRNA). This stand will be synthesized using the minus (-) strand as template by the viral RNA dependent RNA polymerasebrought in the capsid. This newly synthesized strand will serve as mRNA and will be translated to viral proteins including viral enzymesthat will allow the infection process to continue. Note the since the (-) ssRNA cannot serve as mRNA, viral coded proteins such as RNAdependent RNA polymerases cannot be synthesized. Hence this enzyme is brought to the cell in the capsid of the infecting virus and allowfor the synthesis of viral coded proteins required for infection to proceed.

RNAdependentRNApolymerase

Viral (-)ssRNA

(-) ssRNAsynthesizedusing the (+)

strand astemplate.This (-)strand is theprogenynucleic acidthat will beassembledwith the

capsid.

transla

tion

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(+)ssRNA Retrovirus infecting hostcell

(+) ssRNA is reversetranscribed to dsDNA whichis then integrated into thechromosome. Transcriptionthen takes place resulting in(+) ssRNA that serves asmRNA as well as progenyvirus nucleic acid.

Viralparticle

CLASS VI Viruses ± retro viruses (+)ssRNA

Host DNA

Viral (+)ssRNA

(+) ssRNA

Protease

Integrase

Reverse transcriptase

RNAse

Host DNA dependentRNA polymerase

Synthesis of ssDNA byreverse

transcriptase.ThecomplementaryDNA strand isthensynthesizedto give dsDNA

Integration of dsDNA by integrase

Synthesis of (+) ssRNA byhost coded polymerasewhich serves as mRNA aswell as progeny viralnucleic acid

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Class VII dsDNAvirus infecting hostcell

Ds DNA is transcribed to(+)ssRNA (mRNA) which isthen used as template byreverse transcriptase tosynthesize progeny nucleicacid.

Viralparticle

CLASS VII Viruses ± dsDNA viruses thatreplicate using RNA intermediate

Host DNA

ViraldsDNA

Host DNA dependentRNA polymerasedsDNA

translation

Translation of viralcoded proteins suchas reversetranscriptase and

capsids

Synthesis of ssDNA by reversetranscriotase.Complementary

strand is thensynthesized to givedsDNA (progenyviral nucleic acid)

(+) ssRNA

Synthesis of (+) ssRNA(mRNA) byhost

polymerase