INTRO TO VIROLOGY

Question 1

VIRUS DEFINITION AND CHARACTERISTICS

Answer 1

The Virus is a small obligate intracellular parasite that depends on a living host cell for energy, precursors, enzymes and ribosomes to replicate

Consist of a single type Nucleic acid i.e either DNA or RNA (they carry the infectivity of the virus)
A protein coat(capsid) surrounds the nucleic acid
Could be capsulated or non capsulated (enveloped or not)
They’re inert in extracellular environment
The entire infectious unit is called a VIRION i.e (capsid,NA and Envelope or no envelope)

Question 2

THE CAPSID

Answer 2

Functions

1. Prevents Viral RNA from degradation by environmental RNAse
2. Recognizes Cell specific cell membrane receptors in the host cell tissues
3. Penetrating the target cells and delivering the Viral RNA into the cell cytoplasm
4. Selecting and Repackaging cell RNA

Question 3

THE ENVELOPE

Answer 3

Constitutes of Lipid and obtained by budding through a host cell membrane such as the plasma, nuclear or endoplasmic reticular membrane

Allows virus set up persistent infections

Enveloped virus are readily infectious only when the envelope is intact

SURFACE GLYCOPROTEINS of an enveloped virus are important in attachment to cellular receptors on target cells

Question 4

VIRAL ARCHITECTURE AND CLASSIFICATION

Answer 4

3 types
ICOSAHEDRAL: all DNA viruses except Pox virus
HELICAL
COMPLEX e.g Pox virus

CLASSIFIED BASED ON DISEASES
1. Diarrhea inducing: Rotaviruses, enteric adenovirus, astrovirus and calicivirus

2. Respiratory disease virus: Rhinovirus, Adenovirus, Influenza virus, Coxsackie virus, Respiratory syncythial virus
3. Skin diseases virus: poxvirus, papillomavirus, varicella zoster virus
4. CNS- Rabies virus
5. Hepatis— Hbv Hcv Hav Hev Hdv

CLASSIFIED BASED ON NUCLEIC ACID COMPONENT
Single stranded and Double stranded DNA and RNA viruses. Genome of the virus could also be positive or negative

CLASSIFIED AS NAKED OR ENVELOPED

BASED ON ARCHITECTURE

CLASSIFIED INTO FAMILIES (VIRIDAE)
Parvoviridae - human parvovirus B19
Hepadnaviridae - HBV
Papovaviridae - HPV
Adenoviridae - Adenovirus
Herpesviridae - HSV 1&2, EBV
Poxviridae - small pox, cow pox
Picornavoridae - enterovirus and poliovirus 
Caliciviridae - Norwalk
Togaviridae - Rubella virus
Flaviviridae - yellow fever virus
Coronaviridae - coronavirus
Retroviridae - HIV
Rhabdoviridae - Rabies
Paramyxoviridae - measles
Orthomyxoviridae - influenza
Reoviridae - Rotavirus