Viral Gene Expression and Reproductive Cycles

Vocabulary flashcards covering viral life cycles (lytic and lysogenic), prokaryotic and eukaryotic viral genomes, retroviral replication mechanisms, and anti-HIV therapeutics.

Viruses

Infectious agents that cannot reproduce outside of their host cells.

Virions

Viral particles existing outside of host cells that consist of DNA or RNA and a protein coat.

Bacteriophage

A virus that is specific to a bacterium.

Prophage

The viral DNA of a bacteriophage that has integrated into the host chromosomal DNA during lysogeny.

Lytic cycle

A viral reproductive cycle in which the host cell lyses soon after infection to release viral progeny, taking about $30\,\text{minutes}$ from binding to release.

Viral early genes

Genes transcribed by host RNAP that shut down host transcription via negative regulation and stimulate viral genome replication and late gene transcription via positive regulation.

Viral late genes

Genes of the viral genome that encode the viral capsid proteins and enzymes needed to lyse the host cell.

Lysogenic cycle

A viral cycle where viral DNA integrates into the host chromosomal DNA as a prophage and replicates alongside the host for thousands of generations.

DNA viruses

Eukaryotic viruses containing double-stranded or single-stranded DNA used to synthesize a complementary strand in the host cell, capable of both lytic and lysogenic cycles (e.g., Herpes viruses and HPV).

RNA viruses

Viruses usually possessing single-stranded RNA that is translated by the host cell to produce viral proteins involved in RNA replication (e.g., Influenza virus).

Retroviruses

A special class of RNA viruses, such as HIV, containing a gene that encodes the enzyme reverse transcriptase.

Enveloped virus

A virus enclosed in a phospholipid membrane derived from the host cell, such as HIV.

Reverse transcriptase

A viral enzyme carried inside retrovirus virions that uses viral RNA to synthesize a complementary DNA (cDNA) strand.

Integrase

A viral protein carried inside the HIV virion that inserts the viral cDNA into a host chromosome.

Provirus

Viral DNA integrated permanently into the host chromosome, which can remain latent for years.

tat (trans activator of transcription)

A viral protein that binds to viral RNA to dramatically increase the production of full-length viral RNA in HIV.

Anti-HIV drug classes

Therapeutic classes combined to treat AIDS, consisting of reverse transcriptase inhibitors, integrase inhibitors, and protease inhibitors.