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VIRUSES

CLASSIFICATION OF VIRUS ::

1. Holmes in 1948 proposed the classification of viruses. He placed all the viruses into a single order virales, which

is further divided into three sub orders as under. Order Virales

Sub order1

Phagineae

(Bacterial Virus)

Sub order 2

Phytophagineae

(Plant Virus)

Sub order 3

Zoophagineae

(Animal Virus)

First pathogenic animal virus was discovered by Loeffler & Frosch

2. Andre L Woff, Robert Horne and Paul tournier in 1962 proposed a new system of classification of viruses

commonly known as LHT system. This system of classification is mainly based on nuclei acid, symmetry,

number of capsomeres in capsid, shape and size of virus etc. Division – Monera

Class & Microtetobiotes

Order & Virales

Family & Deoxy-ribovira (Viruses with DNA) Ribovira (Viruses with RNA)

3. Some Acellular organisms like Viruses, Viroids as well as Lichens are not included in five kingdom system of

classification.

HISTORY ::

Virus : Latin word, which means "poison" or "venom" or "secretion" (According to Pasture). The first discovered virus → T.M.V. = "Tobacco virus".

A disease is caused by this virus on tobacco plant, is called "Mosaic disease of tobacco".

The first symptoms appears on the leaves of tobacco.

D.J. Ivanowsky separates a micro organism from the sap of infected plant and named "TMV". He reported

that viruses are smaller than bacteria and they can pass through the bacterial proof filters. Davis called them Vitamol. Beijerinck called them living fluid infectant or Contagium vivum fluidum. i.e. infectious living fluid. W.M.Stanley crystallized TMV first time and Nobel prize was awarded to him. (crystal consist of largely

proteins.) Note : (1) Virus : Akaryota group (2) Study of virus : Virology

CHARACTERISTIC FEATURES OF VIRUSES ::

1. These are submicroscopic & acellular organisms generally smaller than 200 mµ/200nm. 2. They are obligate intracellular parasites. 3. They have either RNA or DNA.

No viruses contain both RNA and DNA.

A virus is a nucleoprotein and genetic material is infectious.

4. The can pass through bacterial filters.

5. They have characteristic mode of multiplication, i.e.. Once a virus enters into the host cell, it takes control of whole

biochemical machinery of host cell and directs the metabolic machinery to sythesize their own (viral) components.

Non-living characters of viruses %

1. Absence of protoplasm

2. Absence of enzyme system.

3. No respiration.

4. They can be crystallized like chemicals.

5. They do not grow in culture medium.

6. They are inert out side the host cells.

7. They are autocatalytic and lack fuctional autonomy.

Living characters of viruses %

1. They contain nucleic acid as a result of which they are capable of synthesizing proteins for their coat, although

they use ribosomes of the host for the purpose.

2. They can multiply inside living host cell.

3. They have antigentic properties and shows mutation and specifing to the particular host.

On the basis of above characters it can be said that viruses form a transitional group between living and

non-living

MORPHOLOGY AND STRUCTURE OF VIRUSES ::

Size of Viruses :

TMV – 300 mµ × 20 mµ or 300 × 20 nm

Smallest plant virus : Tobacco necrosis satellite virus (17 nm)

Longest plant virus : Citrus tristeza virus - (2000 × 12 nm)

Smallest animal virus : - Foot & mouth virus – 10 nm

Largest animal virus – Small pox virus (Variola virus) – 400 nm

SHAPE

Brick shaped – Small pox virus

Spherical – Influenza virus, Myxo, Polio, HIV

Rod shaped – TMV

Tadpole like – Bacteriophages.

Bullet shaped – Rabies virus

Chemical composition :

Chemically there are two components of viruses :

(1) Nucleic acid-core

(2) Protein coat.

(1) Nucleic acid : Either RNA or DNA

Generally in plant viruses single stranded RNA is present but in Cauliflower mosaic virus and Potato leaf

roll virus, DNA is present.

Generally in animal viruses either single or double stranded RNA or double stranded DNA is present.

In following animal viruses, RNA is present :

(i) Inluenza virus : Single stranded RNA.

(ii) Rous Scarcoma virus : Single stranded RNA.

(iii) AIDS virus : Single stranded RNA.

(iv) Poliomyelitis virus : Single stranded RNA.

(v) Reovirus : Double stranded RNA.

Single stranded RNA viruses (e.g., AIDS virus) which carrry few molecules of reverse transcriptase enzyme

(which copies RNA into DNA, i.e., reverse transcription), are called retroviruses.

Generally RNA is single stranded but in Reovirus, Wound tumour virus and Rice dwarf virus RNA is

double stranded.

(2) Protein coat :

It is known as capsid and made up of structural units called capsomeres. (Number, size and structure of

capsomeres are vary and these capsomeres are arranged in different manners to form different types of symmetry).

Central core & Capsid are collectively known as nucleocapsid.

Note : An additional covering is also present in some viruses around the caspids. It is composed of Lipo protein.

Such type of vriruses are known as lipovirus.

Example : Myxo Virus and Herpes Virus.

Symmetry of viruses :

1. Helical Symmetry : Capsomeres are arranged in helical manner in the capsid, e.g.. TMV, Influenza virus and

Mumps virus etc.

2. Cuboidal symmetry : Capsomeres are arranged on the surface to form a 20 sided cube, e.g., Turnip Mosaic Virus,

Herpes virus, Adeno virus, Polyoma virus.

3. Complex symmetry : T2. Bacteriophage and Pox virus.

(Tobacco Mosaic Virus) :

It is the most thoroughly studied virus and was discovered by the

Russian worker D. Ivanowsky (1892).

It is rod shaped virus measuring 300 nm × 20 nm

It is having helical symmetry. ࢴ

Having single stranded RNA which is 330 nm in length and

having 7300 nucleotides.

In a capsid number of capsomeres are 2130.

5% RNA and 95% protein → present in TMV.

Influenza virus : Size – 80 – 120 nm

Spherical virus, infecting respiratory tract.

Having helical symmetry, 10% RNA and 90% protein.

Having single stranded RNA, killed at 65ºC and active at low temperature.

Bacteriophage Virus :

Virus which infecting the bacteria. Usually have double stranded DNA

Bacteriophage was discovered by F.W. Twort and Felix d' Herelle

Hershey and Chase discovered heredity material – DNA in T2-bacteriophage through the radio tracer

techniques.

Cyanophage :

The virus which infects blue green algae are known as cyanophage. (Discovered by Safferman and Moris).

Cyanophages contain ds DNA. The structure of cyanophages is similar to the bacteriophages. (Ex. LPP-1

called so as it attacks Lyngbaya, Phormidium and Plectonema)

Sinsheimer : - He discovered single stranded DNA in × 174 bacteriophage. Size – 22 nm :

Capsid

Note :

In bacteriophages, generally DNA is present but in MS2, F2, r-17 bacteriophages, ss RNA is present.

Generally DNA is double stranded but in × 174 bacteriophage and in S13. E. coli phage, DNA is single

stranded.

Types of bacteriophages :

Broadly of 2 types :

1. Prophages or non-virulent phages or non-infective phages : The phages which don't cause lysis of bacteria are

called prophages. Such bacterial cells which are having prophages inside them are called Lysogenic bacteria.

2. Virulent phages or infective phages or, Lytic phase : The phages which cause lysis of bacterial cell at once are

called virulent phages.

Note :

Most studied series of bacteriophages is T-series, i.e., T2, T4, T6, etc. (T-even phages are characterized by angular

head and long contractile tail).

In T3 and T7 bacteriophage head is hexagonal. In T-odd phages tail is short and non-contractile.

Sturcture of bacteriophages :

Having tadpole-like structure and differentiated into head & tail.

Head is prism-like having length 950 Å and breadth 650Å Tail is also

950Å in length, joined to head by neck and collar.

Tail is having hollow core of 80Å and is surrounded by tail sheath.

At the end of tail, end plate is present to which 6 tail fibres are attached,

each is 1500Å in length.

Function of tail fibres :

The tail fibres have two main function : (i) They help in the adsorption

of phage particle on the surface of the bacterium (ii) The enzymes

secreted by these fibres are helpful in the lysis of bacterial cell wall.

NOTE : The water of Ganga is not spoiled due the presence of bacteriophage.

LIFE CYCLE OF BACTERIOPHAGE ::

The life cycle of bacteriophage is also known as infection cycle, which synthesizes many new phage particles

thus, also referred as reproduction (or replication).

The phages reproduce usually by the mean – (i) Lysis (ii) Lysogeny

(i) Lysis/Lytic Cycle :

In this process virus gets attached to the cell wall of bacteria at a spicific place known as receptor site.

At these receptor sties, lysozyme like enzyme synthesized by viruses react with bacterial cell wall.

Consequently, a minute pore is formed through which DNA of the phage enters into the host cell. The empty

capsid and tail fibres left behind are called ghost.

After infection phage DNA assumes control of the cellular metabolism of bacterial cell and directs to

synthesize the phage DNA and proteins.

Subsequently, these new DNA molecules and protein particles assembled to form new bacteriophages which

are liberated in the medium by the endolysis of host cell wall facilitated by the lysozyme like enzyme.

(ii) Lysogeny/Lysogenic cycle : The initiator virus of this cycle is known as temperate phage/-phage

The host cell is not degenerating in this cycle. The DNA of bacteriophage joined with the genophore of

bacterium after the infection and replicates along with this. In this condition it is transmitted to progency of

bacteria. Such virus called as provirus or Porphage. Bacteria which carry a proviruses.

If, it separates from the genophore artificially then it becomes virulent and start the Lytic cycle.

Note :

1. It possible induce lysogenic bacteria to lysis by irradiation with ultraviolet light or by exposure to some

chemical like H2O2.

2. Due to slow reproductive process sometimes, millions of viruses can live their hosts for long period without

any apparent idication of their presence. These are called latent or inapparent infections. [Multiplication of

viral DNA takes place in the latent phage of virus.]

Transduction : When transfer of genetic material from one bacterium (Donor cell) to another bacterium

(receptor cell) takes place by bacteriophage, called as transduction.

Discovered by - Zinder & Lederberg (1952) in Salmonella typhimurium.

1. Generalised transduction : In this type of process bacteriophages are capable to transform any gene of bacteria.

2. Specialized transduction : In this type of process bacteriophages are capable to transform special part of donor

genome.

APPLICATIONS OF PHAGE PARTICLES ::

1. Phages are used in the diagnosis of certain infections.

2. In space microbiology lysogenic cultures are used as radiation detector. They were used by Russians in the space

ship, Vostok-2.

3. Phages are also helpful in the lysis of bacteria present in the polluted water. Hence, they can also be used as

scavengers.

4. Temperate phages help in transduction of genetic material from one bacterial cell to another. They are also used

widely as models in genetic research.

5. Phages are often very harmful as they kill beneficial micro organisms by the Lysigenic activity during process of

manufacture of antibiotics and milk products.

Mycophage :

Viruses, infecting fungi are called mycophages.

Mycophages were first of all discovered by Sinden (1957) in Agaricus bisporus. These are having double

starnded RNA and are spherical or polyhedral/polygonal in shape.

Viroids

T.O. Diener (1971) discovered some new infectious agents, which are still smaller than viruses. These sub-

viral infectious agents are called viroids.

Viroids contain only very low mol. wt. RNA (ss RNA) and not protein coat.

Viroids cause Potato spindle tuber disease, Chysanthemum stunt, Citrus exocortis, Cucumber pale fruit etc.

Viroids cause persistent infections, i.e., never recovered.

NOTE

(i) Due to absence of protein coat viroids are also called as naked virus.

(ii) In viroids RNA, 246 to 388 nucleotides are present. They possesses the power of replication.

Prion or Slow viruses : - Smallest Proteinaceous infectious agent

1. In 1966, three British scientists T. Alper, D. Hagi and M. Clarke discovered infectious agents which were even

smaller than a viriod. They coined the term prion. But credit goes to professor Stanley B.Prusiner for the detailed

study of Prions. Nobel prize was awarded to professor Prusiner in 1997 fot this significant contribution.

2. Prions lack their own genetic material (DNA or RNA). They are consisting of specific protein macro molecules

which is known as prion protein or Prep.

3. According to Prusiner, in most of the animals prion proein is generally associated with the chemical substance

found in the nerve cells of brain.

4. Prions are associated with Kuru (the laughing death) disease of man, Creutzfeldt jakob disease of humans and

animals. Scrapie disease of sheep and goats, mad cow disease.

5. Prion cause diseases of mental disorder.

6. In 1976, D.G. Gajdusek was awarded nobel prize to the research of prion based disease.

PLANT DISEASES CAUSED BY VIRUSES ::

1. Tobacco masaic disease.

2. Leaf curl of papaya.

3. Yellow vein mosaic of lady finger.

4. Potato leaf roll

5. Vein banding mosaic disease of potato

6. Grassy shoot of sugar cane

7. Bunchy top of banana.

8. Turngro disease of rice.

9. Tomato leaf curl.

Note :

1. AIDS virus likes T4-lymphocytes which provide resistance to the organism through production of antibodies. This

virus infects and kills T-lymphocytes (T-helper cells) and hence resistance of host is collapsed. Thus man is

infected with different types of infections. (This is known as Death Warrant.)

2. Dengue fever : Transmitted by Aedes aegypti and Culex fatigans mosquito.

Plant and animal viruses do not have their own infection power.

The plant virus infects with the help of insect – Aphids and animal virus is depend upon Mosquitoes.

Some of virus depend upon other virus for infection. Such viruses are known as satellite virus.

Tobacco satellite virus :

This virus is depend upon tobacco necrosis virus (ss RNA present) for the infection.

Character of viral diseases in plant :

In plants, the symptoms can be Mosaic formation, leaf rolling and curling, yellowing and vein clearing,

dwarfing and stunted growth.

Chlorophyll and other pigments changed into fluid (liquid) through the virus, so the pigments are not

synthesized.

Growth and life duration of the plants reduced.

Bilsters apperars on the leaves and flowers of host due to high growth rate of viruses. So shapes of these

become abnormal.

Due the high metabolic activites, necrosis takes place.

VIRUS : NOMENCLATURE ::

Binominal theory is not applicable on virus. Accroding to Gibbs and Harrison (1968) name of virus is given by

Cryptogram

I pair – Types of Nucleic acid/No. of stand in Nucleic Acid

(D = DNA, R = RNA 1 = Single strand, 2 = Double strand)

II pair – Molecular weight of N. Acid in million/% of Nucleic Acid in virus

III pair – Shape of virus/shape of capsid

(S = Spherical, E = Elongated, X = complex)

IV pair – Types of infected host/Types of vector

(A = Actinomycetes, B = Bacterium, F = Fungus, I = Invertebrates, V = Vertebrates, S = Seed plant)

Cryptogram of TMV – A

S:E

E:5

2:1

R (A = Air)

Influenza virus – A

V:E

S:10

3–2:1

R (A = Air)

Important Point :

Pox virus also known as VIP virus.

Virus which infects yeast – Zymophage.

Cauliflower mosaic virus – ds DNA

PSTV (Potato spindle tuber viroid) – Protein coat is absent

MYCOPLASMA

Systematic position :

Earlier they were included among bacteria. However, in 1966, international committee of Nomenclature of

Bacteria recognised Mycoplasmas as different from bacteria and placed in under a separate class Mollicutes.

The systematic position of Mycoplasma is as below :

Class - Mollicutes

Order - Mycoplasmatales

Family - Mycoplasmataceae

Genus - Mycoplasma

Discovery :

These organism were first discovered by Pasture while studing the causative agent of Bovine

pleuropneumonia in cattle. He could not isolate them in pure culture on standard nutrient media.

In 1898, two French scientists E.Nocard and Roux while studying pleural fluids of cattle suffering from

pleuropneumonia disease, discovered the ogranisms which are known as mycoplasmas and were designated

as PPLO (e.e. Pleuropneumonia like organism).

Nowak (1929) put these organism under the genus Mycoplasma and these organisms are now commonly

called mollicutes (i.e. soft skin).

J. Elford in 1937, isolate these organisms by special type of filters as they could not be separate by bacterial

filters.

The Japaneese Doi et.al. (1967) first discovered that the "Aster yellow" diseases of plants are caused by

Mycoplasma. Doi et.at. named these pleomorphic organisms as mycoplasma like organisms (MLO). According to

DOi, phloem cells (Sieve tube & phloem parenchyma) of plants are much affected by this disease.

These organisms are variously designated as :

1. Cell wall less prokaryotes. 2. Joker of the plant kingdom

3. Joker of the microbiology 4. Coatless bacteria

5. Phytoplasma 6. Glaxoplasma

7. Auxaloplasma 8. Spheroplasma

9. Bedsonia

Structure :

Mycoplasmas are ultramicroscopic, unicellular

and cell wall less organism.

The outer most covering of cell is known as

plasma membrane. It is tri-layered & made up of

lipoprotein (75 Å – 110 Å thickness.)

In cytoplasm, double membrane bound cell

organelles are absent. In cytoplasm, ribosomes

(70S type) are found in granular forms. Protein

occur in soluble forms.

In the middle of the cell occurs a incipient nucleus or nucleoid. The nucleus of this type is devoid of nuclear

membrane and nucleolus.

The amount of double stranded DNA is 4 (mainly) to 6 percent of protoplasm while single stranded RNA is

8 (mainly) to 15 percent of protoplasm.

Mesosomes absent.

NOTE :

1. Three characteristic features of Mycoplasma are :

They are lacking cell wall

Typical colonial appearance.

Filterability through 450 nm bacterial filters (J. Elford – Mycoplasma proof filter)

2. Structurally, Mycoplasma alike as L-form bacteria.

L-typical bacteria = "Lysozyme treated bacteria without cell wall".

Their cell wall is destroyed by the action of lysozyme enzyme.

Gram positive L-typical bacteria are called "Protoplast".

Gram negative L-typical bacteria are called "spheroplast".

3. Important difference between L-forms bacteria and Mycoplasma is that under optimum nutritional conditions.

L-form bacteria will develop cell wall whereas mycoplasma will never develop cell wall.

L-form bacteria was discovered by Klienberger nobel in 1935.

L-for-Lister institute (London), where these bacteria were reported.

Note : -

1. Mycoplasma are non motile, unicellular, smallest ultra microsopic prokaryotic organisms. The diameter of cell

varies from 0.1 µm to 0.3µm.

2. Mycoplasmas may be the simplest form of life capable of independent growth, reproduction and metabolism.

3. They are cell wall less hence, they exhibit pleomorphism and thus called as Joker of plant kingdom.

4. Osmortrophic mode of nutrition is found in Mycoplasma.

5. They requires sterols for their growth in culture medium, because of their cell is unable to synthesize sterols.

such as – cholesterol, ergesterol. (Acholeplasma do not require sterols for their growths)

6. Growth of mycoplasma on solid culture medium – (eg. Agar plate), is like a "fried egg".

7. They are resistant to antibiotics as penicillin, ampicillin, cephaloridine and vencomycin that act on cell wall.

8. They are sensitive to streptomycin, tetracycline & chloramphenicol & erythromycin etc. that act on metabolic

activites.

9. They are gram-ve

Most of the species of Mycoplasma are aerobs or facultative anaerobs i.e., they can survive without oxygen.

. Species of Mycoplasma are saprophyte or facultative parasite.

REPRODUCTION IN MYCOPLASAM ::

1. Binary fission : Most common method of reproduction in Mycoplasma is binary fission.

2. Framgmentation : Specially in filamentous forms.

3. By primary structures (0.1 µ) or "Elementary bodies"

Symptoms of Plant diseases ::

Mycoplasma cuased chlorosis in plants. They destroyed chlorophyll.

Plants becomes dwarf in this disease. The infection of Mycoplasma develops excessive branching. Leaves

becomes small.

Many branches develops from the same place due to the growth of axillary buds. This disease is known as

"witches broom".

(A) Plant disease :

(i) Little leaf of Brinjal.

(ii) Bunchy top of papaya.

(iii) Witche's broom of Ground nut Legume/Potato

(iv) Aster yellow disease of sunflower.

(v) Stripe disease of sugarcane.

(vi) Maize stunt, Clover dwaf, Mulberry dwaf etc.

(vii)Yellow diasease of vinca.

(B) Animal disease : -

(i) Sterility/Genitals inflammation : M.hominis :

This Mycoplasma attacks on germinal epithelium of seminiferous tubules of testis and caused -

(ii) Mycoplasma mycoides causes bovine pleuropneummia.

Note :

Interferons (Antiviral proteins) are formed in the host body by the infection of virus. Which prevents viral

multiplication. In place of these, 'phyto alexins' are formed in plants which prevent the plants from the infection

of viruses, bacteria and fungi.

CULTURE OF MYCOPLASMA ::

These can be cultured in non-living medium although they grow well in living medium conttaining chick tissue.

In non-living medium, they requires cholesterol, ergesterol or agar-agar (obtained from red algae), blood

serum and pH 7.8.

VIRUS (Exercise)

Q.1 "Potato mosaic" disease is caused by : -

(1) Fungi (2) Bacteria

(3) Virus (4) Mycoplasma

Q.2 T.M.V contains : -

(1) Single stranded RNA (2) D.S. RNA

(3) D.S. DNA (4) S.S. DNA

Q.3 Mumps are caused by :-

(1) Bacteria (2) Virus

(3) Rhizopus (4) Animals

Q.4 AIDS is due to : -

(1) Deficiency of T4 –lymphocytes (2) High blood pressure

(3) Deficiency of Riboflavin

(4) Bacterial Infection

Q.5 PSTV have : - (1) Single stranded RNA not enclosed by

protein coat (2) D.S. DNA enclosed by portein coat

(3) Double stranded RNA enclosed by protein

coat

(4) S.S. DNA not enclosed by protein coat

Q.6 AIDS virus contains : -

(1) S.S. RNA with protein (2) D.S. RNA

(3) S.S. DNA (4) D.S. DNA

Q.7 The rabies virus contain : -

(1) S.S. RNA (2) D.S. RNA

(3) S.S. DNA (4) D.S. DNA

Q.8 The protein coat of the virus is called : -

(1) Capsule (2) Pellicle

(3) Capsid (4) Prion

Q.9 The virus without nucleic acid is called : -

(1) Prion (2) Virion

(3) Viroid (4) Venom

Q.10 Which resistant proteins are formed in an

eukaryotic cell due to virus infection : -

(1) Antigens (2) Antibodies

(3) Interferons (4) Auxin

Q.11 Which part of plant is not infected by virus : -

(1) Roots (2) Stem

(3) Leaf (4) Apical meristem

Q.12 Infective unit of virus is called : -

(1) Nucleoid (2) Virion

(3) Nucleo protein (4) Capsid

Q.13 Which bacteriophage have one tail fibers : -

(1) Coliphage

(2) × 174 Bacteriophage

(3) Cyanophage (4) -Phage

Q.14 Match the column-I with column-II and choose

the correct option : -

Column-I Column-II

A. × 174 bacteriophage (i) ds DNA

B. Mycophage (ii) ds RNA

C. Pox virus (iii) ss RNA

D. Polio virus (iv) ss DNA

(1) A – (i) B – (ii) C – (iii) D – (iv)

(2) A – (iv) B – (ii) C – (iii) D – (i)

(3) A – (iv) B – (i) C – (ii) D – (iii)

(4) A – (iv) B – (ii) C – (ii) D – (iii)

Q.15 "Antibiotic" name proposed by : -

(1) A. flamming (2) Waksman

(3) Brein (4) B.M. Duggar

Q.16 Match the column-I with column-II & choose

the correct answer option : -

Column-I Column-II

A.

Prions (I)

Stripe disease of

sugarcane

B.

Viroids (II)

Crysanthemum

stunt

C. Mycoplasma (III) Mad cow disease

D.

Virus (IV)

Tungro disease of

Rice

A B C D

(1) III I II IV

(2) I II III IV

(3) III II I IV

(4) IV II III I

Q.17 Caulimo virus have : -

(1) D.S. RNA (2) S.S. RNA

(3) S.S. DNA (4) D.S. DNA

Q.18 Viroids have : -

(1) DS RNA enclosed by protein coat

(2) DS DNA not enclosed by protein coat

(3) SS RNA enclosed by protein coat

(4) SS RNA not enclosed by protein coat

Q.19 Influenza is caused by : -

(1) Bacillus haemophilus influenza

(2) Pox virus

(3) Myxo virus

(4) Pneumanococcus

Q.20 The literal meaning of virus is a : -

(1) Poison (2) Venome

(3) Secretion (4) All

Q.21 Mycophage have : -

(1) S.S. RNA (2) D.S. RNA

(3) S.S. DNA (4) D.S. DNA

Q.22 Virus are placed in : -

(1) Prokaryota (2) Eukaryota

(3) Akaryota (4) Thallophyta

Q.23 Which character favour nonliving nature of virus : -

(1) Absence RNA

(2) Absence of nuclous

(3) Abiotic state

(4) Ability of reversible crystallization

Q.24 A phage that invades attacks in a host cell but

does not destory it, is know as : -

(1) Temprate phage (2) Sexduction

(3) Phycophage (4) Virulent phage

Q.25 Enzyme synthesis does not occur in : -

(1) Fungi (2) Viruses

(3) Mycoplasma (4) Bacteria

Q.26 Which of the following characters justify the

living nature of viruses : -

(A) Multiplicity

(B) Mutability

(C) Capability of capsid synthesis

(D) All

Q.27 Virus disease do not generally spread through : -

(1) Vegetative propagation

(2) Seeds

(3) Grafting

(4) Cutting

Q.28 Which of the following is absent in virus : -

(1) Mutation (2) Replication

(3) Production of energy (4) All

Q.29 Which of the following is devoid of protein coat

and entirely composed of RNA only : - (1) TMV (2) Pox - virus

(3) PSTV (4) Calimo virus

Q.30 Tailed bacteriophage are : -

(1) Motile on the surface of bacteria (2) Actively motile in liquid water

(3) Motile on the surface of its host

(4) Non motile

Q.31 The smallest disease causing agent is : -

(1) Virion (2) Viriod

(3) Prion (4) Mycoplasma

Q.32 "Scrapie" disease of cattles is caused by : -

(1) Bacterium (2) Virus

(3) Prion (4) Mycoplasma

Q.33 Which part of a virus enters into its host : -

(1) envelope (2) capsid

(3) Nucleic acid (4) All together

Q.34 A mixture of viruses, bacteria & mycoplasma

are boiled in a test tube at 100'C for some time

which of these would survive : -

(1) Virus (2) Bacteria

(3) Mycoplasma (4) All

Q.35 Longest plant virus is : -

(1) f × 174 (2) TMV

(3) Citrus tristeza (4) T1 phage

Q.36 Smallest plant virus is : -

(1) TMV

(2) Citrus tristeza virus

(3) Tobacco necrosis satellite virus

(4) Smallpox virus

Q.37 The infective nature of tobaccro mosaic disease

was discovered by : - (1) I vanowsky (2) Mayer

(3) Beijerinck (4) Stanley

Q.38 Stanley got the nobel prize for : -

(1) Discovering virus (2) Crystallizing virus

(3) Name phages

(4) Discovering antibiotic

Q.39 Cyptogram of TMV is : -

(1) R/2 : 2/5 : E/E : X/S

(2) R/1 : 2/5 : E/E : S/A

(3) R/1 : 1/8 : S/S : S/AP

(4) R/1 : 2/7 : E/E : S/A

Q.40 Phage particles are used as -

(a) Radiation detector (b) Scavengers

(c) Model in genetic research

(1) Only b & c (2) Only a & c

(3) Only c (4) All a, b, c

Q.41 In which of the following DNA is not present : -

(1) Bacteriophage (2) TMV mosaic virus

(3) Mitochondria (4) Chloroplast

Q.42 Which of the following is correct for a virus : -

(1) They have only one type of nuleic acid (2) They replicate inside animal cell only

(3) They are living

(4) They are bigger from bacteria and they

killed them

Q.43 Which of the following is not a viral disease : -

(1) Red Rot of sugarcane & citrus cancer (2) Leaf curl of papaya

(3) Patato leaf roll

(4) Tabacco mosaic

Q.44 Which one of the following pair is related to

viral disease : -

(1) Influenza, mumps, measles

(2) Small pox & chicken pox

(3) Polio & hydrophobia

(4) All of the above

Q.45 HIV attack : -

(1) Epithelial cell (2) Sex cell germinal

(3) B-lymphocytes

(4) T4-lymphocytes

Q.46 Chicken pox is caused by : -

(1) Bacteria (2) Bacteriophage

(3) Varicella virus (4) Pox virus

Q.47 Viral envelope (which is out side the protein

coat) is composed of : -

(1) Protein (2) Lipid

(3) Lipo protein (4) Mucilage

Q.48 Ganga water does not undergo decay due to the

presence of : -

(1) Minerals (2) Antibiotics

(3) Alage (4) Phages

Q.49 Bacteriophage is similar to a fungus &

bacterium in having : - (1) RNA as the genetic material (2) DNA as the genetic material

(3) Cell wall

(4) Similar in reproduction

Q.50 HIV is : -

(1) A single stranded DNA virus (2) A double stranded DNA virus

(3) A single stranded RNA virus (4) A double stranded RNA virus

Q.51 The site where the protein coat (capsid) is

synthesized is : - (1) Plasma membrane of the host (2) Mitochondria of the host

(3) Ribosome of the host

(4) RNA of the virus

Q.52 Which of the following is true for a virus : -

(1) That a virus does not possess D.S. DNA (2) That a virus doest not possess membrane of

lipo-proteins

(3) That a virus does not synthesize enzyme

(4) That a virus does not possess any enzyme

Q.53 Nucleic acid HIV : -

(1) ss RNA (2) ds RNA

(3) ss DNA (4) ds DNA

Q.54 Transduction in bacteria carried out by : -

(1) Bacterio phage (2) B.G.A.

(3) Mycoplasma (4) Rickettssiae

Q.55 During viral infection the protein formed in host

cells to resist is -

(1) Interferon (2) Antitoxin

(3) Antibody (4) Histone

Q.56 Interferons are synthesized in response to

(1) Mycoplasma (2) Bacteria

(3) Viruses (4) Fungi

Q.57 Caulifllower mosaic virus contains : -

(1) ss RNA (2) ds RNA

(3) ds DNA (4) ss DNA

Q.58 Which statement is correct for bacterial

transduction : -

(1) Transfer of some genes from one bacteria to

another bacteria through virus

(2) Transfer of genes from one bacteria to

another bacteria by conjugation

(3) Bacteria obtained is DNA directly

(4) Bacteria obtained DNA from other external

source

Q.59 Tobacco mosaic virus is a tubular filament of

size : -

(1) 300 × 10 nm (2) 300 × 5 nm

(3) 300 × 20 nm (4) 700 × 30 nm

Q.60 Which of the following statements is not ture

for retroviruses : -

(1) Retroviruses carry gene for RNA–dependent

DNA polymerase

(2) The genetic material in mature retrovirsuses

is RNA

(3) Retroviruses are causative agent for certain

kinds of cancer in man

(4) DNA is not present at any stage in the life

cycle of retroviruses.

Q.61 T.O. Diener discovered a : -

(1) Bacteriophage

(2) Free infectious RNA

(3) Free infection DNA

(4) Infectious protein

Q.62 Which of the following is a pair of viral disease ?

(1) Typhoid, Tuberculosis

(2) Ringworm, AIDS

(3) Common Cold, AIDS

(4) Dusentery, Common Cold

Q.63 Nucleic acid is absent in

(1) Virus (2) Viroid

(3) Prion (4) Mycoplasma

Ques. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Ans. 3 1 2 1 1 1 1 3 1 3 4 2 4 4 2 3

Ques. 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Ans. 4 4 3 4 2 3 4 1 2 4 2 3 3 4 3 3

Ques. 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Ans. 3 1 3 3 2 2 2 4 2 1 1 4 4 3 3 4

Ques. 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Ans. 2 3 3 3 1 1 1 3 3 1 3 4 2 3 3

VIRUS EXERCISE

Answer Key

MYCOPLASMA (Exercise)

Q.1 The cell wall less pleomorphic prokaryotic

organism are called : -

(1) Bacteria (2) Virus

(3) Mycoplasma (4) Bacteriophage

Q.2 Plant MLO was discovered by : -

(1) Nocard & Roux (2) Doi and Ishii

(3) Ivanowsky (4) Hershy & Chase

Q.3 Mycoplasma are placed in : -

(1) Eubacteria (2) Mollicutes

(3) Spirochaeta (4) Mycota

Q.4 Which of the following is essential for growth

of mycoplasma in culture media : - (1) N2 (2) Nucleic acid

(3) Cholesterol (4) Lipid

Q.5 Function of elementry bodies in Mycoplasma is : -

(1) Respiration (2) Excretion

(3) Reproduction (4) Food synthesis

Q.6 Mycoplasma infect which tissue in animal

body-

(1) Bone (2) Cartilage

(3) Epithelium (4) Muscles

Q.7 Mycoplasma like mollicutes which do not

require sterols in culture medium are called : -

(1) PPLO (2) MLO

(3) Acholeplasma (4) Spirochaetes

Q.8 Which microbes is capable of growth and

reproduction itself : -

(1) Mycoplasma (2) Virus

(3) Viroid (4) Rib ovirus

Q.9 Who discovered mycoplasma : -

(1) Ivanowsky (2) Lederberg

(3) Nocard & Roux (4) Lister

Q.10 In liquid culture mycoplasma becomes : -

(1) Coccoid in shape (2) Filamentous

(3) Ring shaped (4) Plate like

Q.11 Mycoplasma is a : -

(1) Walled prokaryote (2) Wall less eukaryote

(3) Wall less prokaryote (4) L-form

Q.12 Mycoplasma is : -

(1) Round (2) Pleomorphic

(3) Rod shaped (4) None

Q.13 Mycoplasma is resitant to : -

(1) Pencillin (2) Tetracyclins

(3) Spectinomycin (4) All

Q.14 Mycoplasma generally reproduced through : -

(1) Vegetative method (2) Asexual method

(3) Sexual method (4) Parasexual cycle

Q.15 Mycoplasma differs from virus in being

sensitive to : -

(1) Sugar (2) Protein

(3) Amino acids (4) Tetracyclins

Q.16 Little leaf disease of brinjal is caused by : -

(1) Virus (2) Fungus

(3) Mycoplasma (4) Alage

Q.17 Which of the following is not caused by

mycoplasma : -

(1) Little leaf of brinjal (2) Stub born disease of citrus

(3) Citrus cancer

(4) Witches broom of potato

Q.18 Which mycoplasma cause sterility in human

being : -

(1) M.pneumonia (2) M. hominis

(3) Spiroplasma (4) Thermoplasma

Q.19 Mycoplasma differs from L-forms bacteria in : -

(1) Size of genophore (2) growth

(3) Culture method (4) All of the above

Q.20 In "Aster yello" disease which tissue infected by

mycoplasma is : -

(1) Tracheid (2) Sieve tube

(3) Both (4) None

Q.21 Mycoplasma differ from viruses in : - (1) It requires cholesterol (2) It can be grown on a cell free medium

(3) It is not always parasite

(4) None

Q.22 Mycoplasma neither possess cell wall nor

vacuole & plastid yet it is not included in

animal kingdom because it has : - (1) Genophore

(2) 70 S Ribosome (3) Osmotrophic mode of nutrition

(4) Episome

Q.23 Which is the smallest cellular free living

organsim : -

(1) Yeast (2) Virus

(3) Mycoplasma (4) Bacteria

Q.24 Which of the following is caused by mycoplasma : -

(1) Tuberculosis

(2) Chicken cholera

(3) Pencillin resistant pneumonia

(4) Gangrene

Q.25 Which is/are absent in Mycoplasma : -

(1) Cell wal (2) Chloroplast

(3) Mitochondria (4) All of the above

Q.26 The abbreviation PPLO stands for : -

(1) Pale pneumonia like organism

(2) Pleuro plasma like organism

(3) Pleurisy pneumonia like ogranism

(4) Pleuro pnumonia like organism

Ques. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Ans. 3 2 2 3 3 3 3 1 3 3 3 2 1 1 4 3

Ques. 17 18 19 20 21 22 23 24 25 26

Ans. 3 2 4 2 2 3 3 3 4 4

MYCOPLASMA EXERCISE

Answer Key