Chapter Seventeen: The Simpler Genetic Systems of Viruses and Bacteria

Vocabulary flashcards covering the structural characteristics, taxonomic diversity, reproductive cycles, latency mechanisms, and medical significance of viruses from Chapter 17.

Virus

A small, nonliving infectious particle that consists of nucleic acid enclosed in a protein coat, which must be taken up by a living cell to replicate.

Capsid

The protein coat enclosing a virus's nucleic acid genome, which varies in shape and complexity among different viruses.

Viral Envelope

A structure enclosing the capsid in some viruses that is derived from the host cell plasma membrane and contains viral spike glycoproteins.

Bacteriophage

A virus that infects bacteria; often possesses a complex protein coat with accessory structures such as a head, shaft, base plate, and tail fibers.

Host Cell

A cell that is infected by a virus.

Host Species

A species that can be infected by a specific virus.

Host Range

The spectrum of species and specific cell types that a virus is capable of infecting.

Viral Genome

The genetic material of a virus, which can consist of single-stranded or double-stranded DNA or RNA in a linear or circular form.

Tobacco mosaic virus (structure)

A nonenveloped plant virus characterized by a helical capsid assembled from capsomer protein subunits surrounding a single-stranded RNA genome.

Influenza virus (structure)

An enveloped mammal-infecting virus containing single-stranded RNA and a polyhedral capsid surrounded by a host-derived membrane embedded with spike glycoproteins.

Phage T4 (structure)

A complex double-stranded DNA bacteriophage that infects Escherichia coli, consisting of a polyhedral capsid head, a central shaft, a base plate, and tail fibers.

Integrase

A viral enzyme that cuts host chromosomal DNA and integrates the viral genome into the host chromosome.

Prophage

Phage DNA that has been integrated into the host bacterial chromosome.

Lysogenic Cycle

A viral reproductive cycle in which the viral genome remains integrated as a prophage and replicates alongside the host chromosome over repeated cellular divisions.

Lytic Cycle

A viral reproductive cycle leading directly to the synthesis of viral components, viral assembly, and lysis of the host cell to release progeny viruses.

Lysozyme

A viral enzyme synthesized late in the phage lytic cycle that degrades the host bacterial cell wall, resulting in cell lysis and virus release.

Provirus

Viral DNA that has integrated into the chromosome of a eukaryotic host cell, such as during the reproductive cycle of HIV.

Retrovirus

An RNA virus that utilizes the enzyme reverse transcriptase to synthesize a DNA copy of its genome, which is subsequently integrated into the host cell's DNA.

Reverse Transcriptase

A viral enzyme lacking proofreading function that transcribes viral RNA into complementary single-stranded DNA and then into double-stranded DNA.

Uncoating

The step during viral entry in which host cellular enzymes degrade the capsid proteins to release the viral genome and associated viral enzymes into the cytosol.

Budding

A viral release mechanism in which an assembled capsid pushes through the host cell plasma membrane, acquiring an envelope without immediately lysing the cell.

Viral Latency

A state in which a virus persists in a dormant or inactive condition inside a host cell without causing immediate symptoms or active virus production.

Episome

A viral genetic element that can replicate independently in the host cell but can also occasionally integrate into the host chromosomal DNA.

Emerging Virus

A virus that has arisen recently or shows an elevated probability of causing infectious disease, typically arising through mutations in pre-existing viruses.

Pandemic

An infectious disease outbreak that occurs across a wide geographic region and typically impacts a high proportion of the human population.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

An enveloped, single-stranded RNA emerging virus whose red-colored spike glycoproteins give it a corona appearance, causing the disease COVID-19.

H1N1

A specific mutated strain of the influenza virus that causes swine flu.

Simian Immunodeficiency Virus (SIV)

A virus infecting nonhuman primates in Central and West Africa from which the human immunodeficiency virus (HIV) evolved.

Helper T Cell

A critical mammalian immune white blood cell involved in coordinating immune defenses like antibody production, which is selectively targeted and destroyed by HIV.

Pneumocystis jirovecii

An opportunistic fungal pathogen that causes fatal pneumonia in individuals whose immune systems are compromised by AIDS.

Azidothymidine (AZT)

An antiviral drug that mimics the chemical structure of a normal nucleotide to selectively inhibit HIV reverse transcriptase.

Protease Inhibitors

Antiviral drugs that inhibit viral protease enzymes, preventing the proper assembly of viral capsids and blocking the production of infectious HIV particles.

Vaccine

A biological preparation that stimulates active acquired immunity against a specific infectious disease caused by a virus or bacterium.

mRNA Vaccine

A vaccine type that delivers lipid-nanoparticle-encapsulated mRNA into host muscle cells to direct translation of a viral antigen, such as the SARS-CoV-2 spike glycoprotein.