Lec 8: Classification & Nomenclature

Question 1

Early days of naming was loosely grouped on the basis of criteria such as: (3)

Answer 1

type of host
type of disease caused by infection
type of vectors

Question 2

Later days of naming, based on: (6)

Answer 2

• nucleic acid
• ss/ds
• segmented/non-segmented genome
• virion size
• capsid helical/icosahedral
• virion naked/enveloped

Question 3

ICTV =

Answer 3

“International Committee on Taxonomy of Viruses”

lays down the rules for the nomenclature and classification of viruses.

Question 4

Classification based on genome sequences –>

Answer 4

phylogenetic trees

Question 5

phylogenetic trees show

Answer 5

the degree of similarity between virus genomes, usually generated by computer.

Question 6

2 types of phylogenetic trees

Answer 6

rooted

unrooted

Question 7

Rooted phylogenetic trees =

Answer 7

the tree begins at a root which is assumed to be the ancestor of the viruses in the tree.

Question 8

Unrooted phylogenetic trees =

Answer 8

no assumption is made about the ancestor of the viruses in the tree.

Question 9

Bacterial viruses –>

Answer 9

allotted codes, such as T1, T2 and ϕX174.

Question 10

Viruses of humans and other vertebrates were commonly named after:

Answer 10

• the diseases that they cause (ex: measles virus, smallpox virus)
• the city, town or river where the disease was first reported (ex: Newcastle disease virus, Norwalk virus, Ebola virus)

Question 11

Insect viruses –>

Answer 11

named after the insect, with an indication of the effect of infection on the host,
e.g. Autographa californica nuclear polyhedrosis virus (virus was isolated from Autographa californica larvae that had large polyhedral structures in the nuclei of infected cells.)

Question 12

plant viruses –>

Answer 12

the host and signs of disease,

e.g. potato yellow dwarf virus, tobacco rattle virus.

Question 13

An advantage of the Baltimore classification is

Answer 13

its differentiation between (+) RNA viruses that do (class 6) and do not (class 4) carry out reverse transcription, 
and between dsDNA viruses that do (class 7) and do not (class 1) carry out reverse transcription

Question 14

Bacterial viruses –>
Plant viruses –>
Most vertebrate viruses –>

Answer 14

• codes
• host and signs of disease
• diseases that they cause, or the locations where the disease was first reported