Introduction To Virology Flashcards
Virion
Non-living particle composed of genetic material and capsid outside the host cell and capable of becoming active (infective) in living host cells
Viruses
Are acellularsubmicroscopic organisms made up of genetic materialsurrounded by a protein coat (capsid) capable of becoming active in living cell
Viruses may have an extra outer covering of the capsid (envalop) or may not (naked)
Viruses as non-living
Viruses first exist as non-living particles in the environment referred to as Virion.
- A virionfunctions to protect the genome inside it and delivers it into a suitable host cells for replication.
- Viruses are acellularorganisms (no true cell). That is, they lack true cell organelles such as ribosomes, mitochondria, golgibodies, endoplasmic reticulum, e.t.c.
- Viruses are completely dependent on host cell for activation and replicatio
Viruses as living things
•Every virus has a genome (code of life) which is activated upon entry into a host cell and begins the process of
replication.
•Although, viruses lack protein synthesizing machinery, they contain structures needed to evade host cells and manipulate the cell replicating machinery into producing more copies of the virus rather than normal cellular proteins.
Size and Scale of Viruses
- Viruses are the smallest living organism inside a host cell capable of replication.
- Usually measured in nanometers (nm)1 nm = 10-9 metres
- Viruses range in size from 20nm to few millimetres. Approximately 1/1000thof a bacteria.
- Visualized mainly with the use of an electron microscope
Viruses as Ubiquitous
; can be found everywhere on earth in soil, water, and air in reasonable mount.
•Scientist have observed that the intensity of studying a living species is directly proportional to the discovery of new viral species.
Implies that the more we study a species, the more virus we may find
Viruses as intracellular parasites
what 3 things are they dependent on the host for?
- They manipulate host cell genetic machinery for the synthesis of new viral genome through a process called Replication.
- As parasites, they are dependent on host for the following:
- building blocks (e.g. Amino acids and nucleosides)
- machinery for protein synthesis such as ribosomes
- energy (ATP) for DNA or RNA synthesis.
•Viruses can modify host cells to produce proteins that are used as membrane structure or dampen immune response against i
Genetic code of Viruses
A virus has Genewhich is either DNA or RNA. Different from cellular organisms whose genetic unit is a DNA.
•Viruses can be divided into four groups of based on the number of strand in its genome.
- double-stranded DNA (dsDNA)
- single-stranded DNA (ssDNA)
- single-stranded RNA (ssRNA)
- double-stranded RNA (dsRNA)Note that groups 2-4 are unique to viruse
Satellite Viruses
. Certain viruses are referred to as Satelliteviruses, because they require the host to be infected with a second strain of virus known as helpervirus before becoming infective.
•Asatellite virus lacks one or more functions needed for replication which is provided by the helper virus.
•Examples:
1.Hepatitis delta virus (ssRNA) in an animal host needs a Hepatitis B virus (dsDNA) to replicate.
- Enterobacteriaphage P4 (dsDNA) in a bacterium needs an Enterobacteriaphage P2 (dsDNA) to replicate.
- The satellite tobacco necrosis virus (ssRNA) in plant needs a tobacco necrosis virus (ssRNA) to replicate.
Viruses as agents of economic loss
- Outbreak of virus infection such as SAR-COV-2 have resulted in huge economic losses worldwide worth billions of dollars.
- In the fermentation industry, bacteriophages can kill the lactic acid bacteria that triggers the production of yogurt, cheese and other dairy products.
- Also, bacteriophages can disrupt the industrial production of amino acid by killing the Corynebacteriumspecies involved in the fermentation process
Viruses in Biotech
Knowledge about the biology of viruses have helped man develop various molecules to help improve and sustain lives as follows:
- Pioneer in molecular biology discoveries: In 1952, Alfred Hershey and Martha Chase, employed phage T2 and E. coli to show concrete evidence that the genetic material is made up of DNA.
- Vectors for gene in protein production: Some baculovirusesand adenoviruses are used as gene carriers into plant or animal cells for mass protein production.
Viruses as Vectors for gene for treatment of genetic disease
es: Retroviruses have been employed as gene carriers to treat Severe Combined Immunodeficiency genetic disease in childre
Viruses as sources of enzymes
s: Certain virus enzymes have been employed in molecular biology. E.g. Phage RNA polymerases have been employed in the synthesis of RNA while reverse transcriptasesfrom retroviruses have been used in the DNA synthesis
Viruses for characterization of bacteria
: Certain groups of bacteria (Salmonellaspecies) have been categorized into strains based on the type of phage present and have been used in the identification of bacteria during an outbreak.
Viral Pesticides
: baculoviruseshave been employed as bio-control agent against some insect pest
