Negative single-stranded RNA (-ssRNA) viral genomes cannot be directly translated by host ribosomes. Instead, the virus must bring its own RNA-dependent RNA polymerase (RdRP) to transcribe the -ssRNA genome into a complementary positive single-stranded RNA (+ssRNA) strand, which is then translated by host ribosomes.

Replication of -ssRNA Animal Viruses

During the replication of double-stranded RNA (dsRNA) animal viruses, the viral enzyme RNA-dependent RNA polymerase (RdRP) uses the negative strand of the double-stranded genome as a template to synthesize positive single-stranded RNA (+ssRNA) strands, which are then translated by host cell ribosomes.

Replication of dsRNA Animal Viruses

An RNA-dependent RNA polymerase (RdRP) is a viral enzyme that synthesizes a complementary RNA strand from an RNA template, enabling the replication and transcription of viral RNA genomes.

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During the replication of animal viruses in eukaryotic host cells, the site of genomic replication depends on the nucleic acid type: most DNA viruses replicate their genomes within the cell nucleus, whereas most RNA viruses replicate within the cytoplasm.

Nucleic acid biosynthesis of Animal Viruses

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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While most DNA viruses replicate inside the host cell's nucleus, large DNA viruses, such as poxviruses, are exceptions that replicate within the cytoplasm.

Cytoplasmic Replication of DNA Viruses

While RNA viruses that infect animal cells generally replicate in the cytoplasm, the influenza virus is a notable exception to this replication location.

Exception to RNA Animal Virus Replication Location

RNA-dependent RNA Polymerase

If an animal virus has a positive single-stranded RNA (+ssRNA) genome, its genomic RNA acts similarly to cellular mRNA and can be translated directly by host ribosomes to synthesize viral proteins.

Replication of +ssRNA Animal Viruses

If an animal virus has a single-stranded DNA (ssDNA) genome, host enzymes synthesize a complementary second strand to produce double-stranded DNA (dsDNA). This double-stranded DNA is then replicated, transcribed, and translated in the same manner as host cell DNA.

Replication of ssDNA Animal Viruses

Reverse transcriptase is a viral enzyme carried within the capsid of retroviruses, such as HIV, that synthesizes a complementary single-stranded DNA (cDNA) copy using the viral positive single-stranded RNA (+ssRNA) genome as a template.

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