Micro Ch. 11

Hepadnavirus

A virus with a partially double-stranded DNA genome

Negative strand

An RNA strand that serves as a template for making a complementary RNA strand

Positive strand

An RNA strand that can be directly used as mRNA

Prion

An infectious protein that contains no nucleic acid

Retrovirus

An RNA virus that uses reverse transcription during replication

Reverse transcription

The process of making DNA from an RNA template

RNA replicase

An enzyme that makes RNA from an RNA template

Viroid

A small, circular, single-stranded RNA molecule that infects plants, no capsid

Positive vs. negative-strand RNA viruses

Positive-strand RNA acts as mRNA; negative-strand RNA must be copied into positive RNA first.

mRNA production in single-stranded RNA viruses

Positive-strand viruses use RNA directly; negative-strand viruses use RNA replicase to make mRNA.

Genetic information flow in retroviruses

They make DNA from RNA using reverse transcriptase.

Unique features and damage of Pox viruses

They replicate in the cytoplasm and can cause tissue damage and cell death.

Location of adenoviruses in the body

Respiratory tract and intestinal tract.

Diseases caused by herpesviruses

Cold sores and genital herpes.

Disease associated with coronaviruses

COVID-19.

Rabies virus shape and type

Bullet-shaped rabies virus; negative-strand RNA virus.

Antigenic shift and drift

Shift = major change from reassortment; drift = small mutations. Both occur in influenza viruses.

Reoviruses

Double-stranded RNA viruses.

HIV type and disease

Retrovirus; it causes AIDS.

Host cell for hepadnaviruses

Liver cells (hepatocytes).

Viral replication comparison

DNA viruses copy DNA; RNA viruses copy RNA; retroviruses copy RNA into DNA.

Viroids and their hosts

Small circular RNA molecules that infect plants.

Differentiation of prions from other agents

They contain protein but no nucleic acid.

Native vs. pathogenic prion proteins

The pathogenic form has a different protein shape and causes normal proteins to misfold.

Prion vs. viroid vs. virus

Prion = infectious protein; viroid = infectious RNA; virus = nucleic acid inside a protein coat.

Prion diseases and organisms

Creutzfeldt-Jakob disease (humans), scrapie (sheep/goats), and mad cow disease (cattle).

Viruses associated with antigenic drift and shift

Influenza virus.

Viruses directly used for translation

Positive ssRNA.

Cause of mad cow disease

Prions which are infectious proteins.

Disease NOT caused by herpes viruses

Spongiform encephalopathy.

Envelope of an animal virus

Made from the cell membrane as the virus buds out of the host.

Normal function of the PrP protein

Assisting in normal synaptic development and function.

Normal vs. infectious prion proteins

Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.

Multiplication of infectious prions

Prions transform normal proteins into the misfolded beta-pleated sheet configuration through conversion.

Pathogenicity of beta-pleated PrP multimers

The multimers are more stable and resistant to protease.

Prion disease found in deer and elk

Chronic wasting disease.

Prion disease known as laughing disease

Kuru.

Human condition linked to bovine spongiform encephalopathy

Variant Creutzfeldt-Jakob disease.

Nervous system part affected by fatal familial insomnia

Thalamus.

Origin of the name "scrapie"

The prion disorder causes infected sheep to scrape against objects until their skin is raw.

Derivation of the term "prions"

Proteinaceous infectious particles.

Year of prion discovery

1982 by Stanley Prusiner.

First prion disease identified by Stanley Prusiner

Scrapie.

How prions differ from other infectious agents

They lack nucleic acid.

Purpose of synthesizing a negative RNA strand in positive ssRNA viruses

To serve as the complementary template for making more positive-strand RNA.