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Past systems of classification

Viruses are classified in several ways: by factors such as their core content ( [link] and [link] ), the structure of their capsids, and whether they have an outer envelope. The type of genetic material (DNA or RNA) and its structure (single- or double-stranded, linear or circular, and segmented or non-segmented) are used to classify the virus core structures.

Virus Classification by Genome Structure and Core
Core Classifications Examples
  • RNA
  • DNA
  • Rabies virus, retroviruses
  • Herpesviruses, smallpox virus
  • Single-stranded
  • Double-stranded
  • Rabies virus, retroviruses
  • Herpesviruses, smallpox virus
  • Linear
  • Circular
  • Rabies virus, retroviruses, herpesviruses, smallpox virus
  • Papillomaviruses, many bacteriophages
  • Non-segmented: genome consists of a single segment of genetic material
  • Segmented: genome is divided into multiple segments
  • Parainfluenza viruses
  • Influenza viruses
Part a (top) is an illustration of the rabies virus, which is bullet-shaped. RNA is coiled inside a capsid, which is encased in a matrix protein-lined viral envelope studded with glycoproteins. Part a (bottom) is a micrograph of a cluster of bullet-shaped rabies viruses. Part b (top) is a micrograph of variola virus, which has DNA encased in a bow-shaped capsid. An oval matrix protein-lined envelope surrounds the capsid. Part b (bottom) shows irregular, bumpy lesions on the arms and legs of a person with smallpox.
Viruses are classified based on their core genetic material and capsid design. (a) Rabies virus has a single-stranded RNA (ssRNA) core and an enveloped helical capsid, whereas (b) variola virus, the causative agent of smallpox, has a double-stranded DNA (dsDNA) core and a complex capsid. Rabies transmission occurs when saliva from an infected mammal enters a wound. The virus travels through neurons in the peripheral nervous system to the central nervous system where it impairs brain function, and then travels to other tissues. The virus can infect any mammal, and most die within weeks of infection. Smallpox is a human virus transmitted by inhalation of the variola virus, localized in the skin, mouth, and throat, which causes a characteristic rash. Before its eradication in 1979, infection resulted in a 30–35 percent mortality rate. (credit “rabies diagram”: modification of work by CDC; “rabies micrograph”: modification of work by Dr. Fred Murphy, CDC; credit “small pox micrograph”: modification of work by Dr. Fred Murphy, Sylvia Whitfield, CDC; credit “smallpox photo”: modification of work by CDC; scale-bar data from Matt Russell)

Viruses can also be classified by the design of their capsids ( [link] and [link] ). Capsids are classified as naked icosahedral, enveloped icosahedral, enveloped helical, naked helical, and complex ( [link] and [link] ). The type of genetic material (DNA or RNA) and its structure (single- or double-stranded, linear or circular, and segmented or non-segmented) are used to classify the virus core structures ( [link] ).

The left illustration shows a 20-sided structure with rods jutting from each apex. The right micrograph shows a cluster of adenoviruses, each about 100 nanometers across.
Adenovirus (left) is depicted with a double-stranded DNA genome enclosed in an icosahedral capsid that is 90–100 nm across. The virus, shown clustered in the micrograph (right), is transmitted orally and causes a variety of illnesses in vertebrates, including human eye and respiratory infections. (credit “adenovirus”: modification of work by Dr. Richard Feldmann, National Cancer Institute; credit “micrograph”: modification of work by Dr. G. William Gary, Jr., CDC; scale-bar data from Matt Russell)
Virus Classification by Capsid Structure
Capsid Classification Examples
Naked icosahedral Hepatitis A virus, polioviruses
Enveloped icosahedral Epstein-Barr virus, herpes simplex virus, rubella virus, yellow fever virus, HIV-1
Enveloped helical Influenza viruses, mumps virus, measles virus, rabies virus
Naked helical Tobacco mosaic virus
Complex with many proteins; some have combinations of icosahedral and helical capsid structures Herpesviruses, smallpox virus, hepatitis B virus, T4 bacteriophage

Questions & Answers

Ayele, K., 2003. Introductory Economics, 3rd ed., Addis Ababa.
Widad Reply
can you send the book attached ?
Ariel
?
Ariel
What is economics
Widad Reply
the study of how humans make choices under conditions of scarcity
AI-Robot
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn Reply
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn
what is ecnomics
Jan Reply
this is the study of how the society manages it's scarce resources
Belonwu
what is macroeconomic
John Reply
macroeconomic is the branch of economics which studies actions, scale, activities and behaviour of the aggregate economy as a whole.
husaini
etc
husaini
difference between firm and industry
husaini Reply
what's the difference between a firm and an industry
Abdul
firm is the unit which transform inputs to output where as industry contain combination of firms with similar production 😅😅
Abdulraufu
Suppose the demand function that a firm faces shifted from Qd  120 3P to Qd  90  3P and the supply function has shifted from QS  20  2P to QS 10  2P . a) Find the effect of this change on price and quantity. b) Which of the changes in demand and supply is higher?
Toofiq Reply
explain standard reason why economic is a science
innocent Reply
factors influencing supply
Petrus Reply
what is economic.
Milan Reply
scares means__________________ends resources. unlimited
Jan
economics is a science that studies human behaviour as a relationship b/w ends and scares means which have alternative uses
Jan
calculate the profit maximizing for demand and supply
Zarshad Reply
Why qualify 28 supplies
Milan
what are explicit costs
Nomsa Reply
out-of-pocket costs for a firm, for example, payments for wages and salaries, rent, or materials
AI-Robot
concepts of supply in microeconomics
David Reply
economic overview notes
Amahle Reply
identify a demand and a supply curve
Salome Reply
i don't know
Parul
there's a difference
Aryan
Demand curve shows that how supply and others conditions affect on demand of a particular thing and what percent demand increase whith increase of supply of goods
Israr
Hi Sir please how do u calculate Cross elastic demand and income elastic demand?
Abari
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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