Viruses and Other Non-Cellular Entities

Comprehensive vocabulary flashcards covering viral history, morphology, classification, replication cycles, vaccines, and other non-cellular pathogens like prions and viroids.

Louis Pasteur (1884)

The scientist who first proposed the term "virus," which is the Latin word for poison.

Edward Jenner (1796)

The individual who created the first vaccine against a virus to prevent Smallpox.

Tobacco Mosaic Virus

The virus identified in plants during the 1890s by Ivanowski and Beijerinck.

Devolution/Regressive Hypothesis

The evolutionary hypothesis suggesting that viruses evolved from prokaryotic cells.

Escapist/Progressive Hypothesis

The hypothesis suggesting viruses evolved from DNA and/or RNA, or viroids that escaped from a host cell.

Virion

A single viral particle, often referred to as an infectious particle or entity.

Obligate Pathogens

Entities that cannot survive without host cells because they require the host's metabolic and reproductive machinery.

Nucleocapsid

The structure consisting of the nucleic acid core and the protein capsid shell found in all viruses.

Capsomeres

The repeating protein subunits that make up the protein capsid shell.

Spikes (Glycoproteins)

External protein receptors that act as molecular keys to allow the virion to gain entry into a host cell.

Bacteriophage

A virus that infects a bacterial cell, typically featuring an icosahedral capsid containing $dsDNA$ and a bottom section with landing legs.

RNA Virus Mutations

Occur more frequently because RNA polymerase is less accurate than DNA polymerase, making these viruses more capable of adaptation.

Baltimore Classification

A classification system that groups viruses (I through VII) based on their mode of mRNA production.

ICTV

The International Committee on Taxonomy of Viruses, which enforces modern standards of nomenclature.

-viridae

The suffix required for the name of a viral family (e.g., Coronaviridae).

Adsorption

The first step of viral infection involving specific attachment via spikes to host-cell receptors.

Uncoating

The third step of viral infection where the viral genome is released from the capsid.

Synthesis in DNA Viruses

A process that must occur inside the host cell's nucleus using the host's enzymes for replication and transcription.

Proviruses

Latent viruses where the DNA inserts itself into the host chromosome for later excision, such as Herpes Simplex 1 & 2.

Oncoviruses

Viruses whose DNA insertion into the host chromosome causes changes that lead to cancer, such as HPV.

Reverse Transcriptase

An enzyme carried by retroviruses like HIV to turn its RNA into $cDNA$.

Prophage

The state of phage DNA when it integrates into a bacterial chromosome during the lysogenic cycle.

Nosocomial Infections

Pathogens commonly found in and acquired within healthcare settings.

Zoonoses

Infectious diseases that spillover from animal to human populations due to mutations like antigenic shift.

Herd Immunity

Occurs when a certain percentage of a population is immune, preventing the pathogen from transmitting person-to-person.

Inactivated Vaccines

Vaccines where the entire microbe is present but destroyed by heat, chemicals, or radiation (e.g., Polio, injected Flu).

Live Attenuated Vaccines

Vaccines where the entire microbe is functional and capable of replication but altered to not cause disease (e.g., Measles).

Heterotypic/Jennerian Vaccines

Vaccines where a live microbe that causes an animal version of a disease is inoculated into a human to impart immunity (e.g., original Smallpox vaccine).

Prions

Misfolded proteins that cause plaque build-up in the central nervous system and are responsible for diseases like Mad Cow Disease and Kuru.

Viroids

The smallest pathogens on Earth, consisting of small, circular $ssRNA$ molecules without a protein capsid that only infect plants.