Topic 2: General Virology Flashcards
What is a virus?
• Entities that whose genomes are elements of nucleic acid that replicate inside living cells using the cellular synthetic machinery and causing the synthesis of specialised elements that can transfer the viral genome to other cells
• Viruses are small:
- Chlamydia sp. ~ 400nm
- Poxvirus ~ 400nm
- Herpesvirus ~ 200nm
- Picornavirus ~ 30nm
• Need living cells to replicate
• Lack organelles
• Consist of either DNA, RNA or both
• Have a protective protein coat – “capsid”
• Replicate only within cells of hosts they infect
• Completely dependent on the metabolic machinery of the host cell for reproduction
How do viruses differ from other micro-organisms?
• A fully assembled virus is termed a virion
• Process only biophysical properties and additional characteristics which become evedent when it infects a susceptible host cell
• Contains a nucleoprotein core – to infect and replicate inside a host cell
• The genome of vertebrate viruses is inside a capsid – each subunit contains a polypeptide chain
• Haploid except in retroviruses
• Shape is always symmetrical
- Icosahedral
• Closed shell virons
• Isometric viruses
• Gives a overall stronger shape and maximum capcity
- Helical
• Condensed nucleic acid incorporates into histones
• Basic encoded-virus molecules
• RNA viruses are inserted between protein units
• Each capstone consists of a single polypeptide molecule
• Enveloped viruses are covered in a lipid bilayer and associated glycoproteins
- Required for:
• Endoplasmic reticulum
• Golgi apparatus
• Nuclear membrane
- Allows compartmentalization of the host cell
- Binds to receptors on host cells, membrane fusion, uncoating of a viron and destruction of receptors on host cells
Describe the components of a virus
• Consists of: - Nucleic acid genome (DNA, RNA or both) - Enclosed in a protein coat “capsid” - Made up of subunits “capsomers” - +/- within a envelope (modified host membrane) • Anatomy of: - Parvovirus • Non-enveloped • Isometric capsid symmetry • Ss linear DNA genome - Paramyxovirus • Enveloped • Helical capsid symmetry • (-) ss RNA genome - Poxvirus • Enveloped • Complex morphology • Linear ds DNA genome • Non-enveloped viruses - Adenovirus
Have a broad understanding of viral taxonomy
• Genome - Nucleic acid characteristics • Type (RNA, DNA) • Size • Single or double stranded • Circular or linear • # Of nucleic acid molecules in viron • Nucleotide sequence • Presence of characteristic open reading frames (ORF) • Morphology of the viron - Shape and size - # Of capsomers - +/- of an envelope • Mode of replication • Presession of characterics enzymes - Reverse transcriptase - Neuraminidase
