Test: Virus - Class 11 MCQ

The primary pathogen is Potato Virus Y (PVY) which may act alone or in conjunction with PVX. There are many strains of PVY with differing characteristics and behavior. PVY is spread by both seed and aphids. Control requires certification, roguing and aphid control.

Tobacco mosaic virus (TMV) is a positive-sense single-stranded RNA virus. TMV is composed of RNA and protein. Tobacco mosaic virus has a rod-like appearance. Its capsid is made of coat protein and one molecule of genomic single strand RNA, 6400 bases long.

Mumps is due to an infection by the mumps virus. It can be transmitted by respiratory secretions (e.g. saliva) from a person already affected with the condition. When contracting mumps, the virus travels from the respiratory tract to the salivary glands and reproduces, causing the glands to swell.

Option (a) deficiency of T4 - lymphocytes is the correct answer. 

Explanation :- 

AIDS - Acquired immuno deficiency virus syndrome

Is neither due to any bacterial infection  nor dye to high blood pressure.  Also it is not due to deficiency of riboflavin. 

Because, Riboflavin deficiency results into  stomatitis including painful red tongue with sore throat and inflammation of the corners of the mouth. 

But the deficiency of  T4 - lymphocytes causes immunodeficiency of cell mediated immunity. 

So, the correct answer is option (a)

PSTV is potato spindle tuber viroid. It is to be identified as a small, single stranded circular RNA molecule. It does not enclosed in a protein coat.
Mostly viroids shows these characters.

Shortly after the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the positive-sense single-stranded RNA genome from the attached viral proteins and copies it into a complementary DNA (cDNA) molecule. The integrated viral DNA may then lie dormant, in the latent stage of HIV infection.

The rabies virus is a negative-sense, non-segmented, single-stranded RNA virus measuring approximately 60 nm × 180 nm. It is composed of an internal protein core or nucleocapsid, containing the nucleic acid, and an outer envelope, a lipid-containing bilayer covered with transmembrane glycoprotein spikes. Hence, Option A.

A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic material of the virus.

Prions, so-called because they are proteinaceous, are infectious particles, smaller than viruses, that contain no nucleic acids (neither DNA nor RNA).

Interferons (IFNs) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten their anti-viral defenses.

The actively growing regions of a plant, such as the plant meristems remain free of infections even when the plant itself is infected. Tissues from shoot apical meristem can be taken and cultured to grow roots and obtain new plants. Therefore virus-free plants can be obtained from the meristematic tissues of the plant. 
So, the correct option is 'Apical Meristem'.

A complete virus particle, known as a virion, consists of nucleic acid surrounded by a protective coat of protein called a capsid. These are formed from identical protein subunits called capsomeres. Viruses can have a lipid "envelope" derived from the host cell membrane.

Enterobacteria phage λ (lambda phage, coliphage λ, officially Escherichia virus Lambda) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). It was discovered by Esther Lederberg in 1950. The phage particle consists of a head (also known as a capsid), a tail, and tail fibers. The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell.

Bacteriophage ϕ×174 is a single-stranded DNA virus that infects Escherichia coli, and the first DNA-based genome to be sequenced. Its DNA is composed of 5386 nucleotides.
Mycophage is a virus, the host of which is a fungus, in contradistinction to a bacteriophage, the host of which is a bacterium. It has dsRNA as genetic material.
Vaccinia virus (VACV) is a well studied poxvirus. It has a dsDNA genome that is expressed and replicated in the cytoplasm of host cells.
Poliovirus is a single-stranded RNA virus. Thus, the genome enclosed within the viral particle can be used as messenger RNA and immediately translated by the host cell.

The word 'antibiotics' was first used by the Ukrainian-American inventor and microbiologist Selman Waksman, who in his lifetime discovered over 20 antibiotics.

Mad cow" disease is an infectious disease caused by prions that affect the brains of cattle. The actual name of the disease is bovine spongiform encephalopathy (BSE), a name that refers to the changes seen in brain tissue of affected cows.
Several pathogens, including viruses, viroids, and phytoplasma, cause serious diseases in chrysanthemums. So far, ten species including Chrysanthemum stunt viroid (CSVd) and Potato spindle tuber viroid (PSTVd) are members of the genus Pospiviroid.
Mycoplasma is a genus of the bacteria which infects plants, animals and humans causing diseases. Some of the common diseases in plants caused by Mycoplasma are citrus greening, sandal spike and grassy shoot in sugarcane plant. In citrus greening, the fruits are small and green in colour. In sandal spike, there is a reduction in leaf size and formation of rosette spike. In the grassy shoot, there is an overgrowth of leaves and there is no growth of cane.
Rice tungro disease is caused by the combination of two viruses, which are transmitted by leafhoppers. It causes leaf discoloration, stunted growth, reduced tiller numbers and sterile or partly filled grains. Tungro infects cultivated rice, some wild rice relatives and other grassy weeds commonly found in rice paddies.

Cauliflower mosaic virus (CaMV) is a member of the genus Caulimovirus. It is one of the viruses which infect many plants especially the members of Cruciferae. It contains DNA as a genetic material instead of RNA and replicates through the mechanisms of reverse transcription like a retrovirus. Thus, the correct answer is option D.

Viroids are generally known as plant pathogens. They are small, single-stranded, circular RNA particles. They do not have a capsid or outer envelope of protein making them simpler than virus, but like viruses, can reproduce only within a host cell. They do not have capacity to make their own protein. They produce only a single, specific RNA molecule. Thus, the correct option is 'ssRNA not enclosed by a protein coat.'

Bacillus haemophilus or Bacillus influenzae is a Gram-negative, facultatively anaerobic bacteria that causes influenza disease. It was first described by Richard Pfeiffer during an influenza pandemic. It is usually present in the upper respiratory tract and causes otitis media, epiglottitis, and meningitis.

Virus, an infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria. The name is from a Latin word meaning “slimy liquid” or “poison.”

Virus is a microscopic particle that can infect the cells of a biological organism. Akaryota Viruses can only replicate themselves by infecting a host cell and therefore cannot reproduce on their own.

Viruses are ultramicroscopic disease producing organisms. They have two fundamental characteristics of living system i.e. presence of nucleic acid as genetic material and the ability to produce their  own copies. They have no cellular organization and no metabolic machinery of their own. They are obligatory intracellular parasites as they are completely inactive outside the host.
They can be crystallized and even in their crystalline form, they retain their infectivity. Wendall Stanley was the first to purify and crystallize a plant virus called Tobacco Mosaic Virus (TMV) and he showed that even in crystalline form the virus retains it's infectivity. This showed the non living nature of the virus.
So, the correct answer is D.

Virulent phage exhibits lytic cycle that includes multiplication of viral particles followed by disruption of the host cell to release the virions. Temperate phage exhibits lysogeny, the phase of virus that does not lyse the host cell and remain inactive. The term “phycophage” refers to viruses that affect fungi. Thus, the correct answer is option A.

Without a host cell, viruses cannot carry out their life-sustaining functions or reproduce. They cannot synthesize proteins, because they lack ribosomes and must use the ribosomes of their host cells to translate viral messenger RNA into viral proteins.

Characters of living nature of viruses are: Viruses have genetic material (DNA or RNA). They can mutate. They can grow, once inside the host cell. They can be transmitted from one host to another. They are capable of multiplication within a host. They react to heat, radiation and chemicals. They show irritability. They bring about enzymatic changes in vitro. They are able to infect and cause the disease to living beings. The DNA and proteins of viruses are similar in composition and structure to those of higher organisms. Thus, the correct answer is option D.

The viral disease is caused due to infection of pathogenic virus that attacks the cells. Transmission of plant viruses is through the transfer of sap, insects, nematodes, plasmodiophorids, seed and pollen and direct plant to human transmission.  However, the spread of virus does not take place through vegetative propagation. Thus, the correct answer is option B.

A virus is a small infectious agent, that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from plants and animals to micro-organisms, including bacteria and archae. Viruses can undergo replication by lytic and lysogenic cycles. The feature of viruses to perform viral genetic change in their own genome is a process of virus mutation. Viral proteins can be synthesized in host cells by using host machinery. Energy production and liberation process is absent in viruses, as this process is not required by viruses. Thus, option C is correct.

Poxvirus consists of a nucleoprotein core which contains double-stranded DNA coated by different types of proteins maintaining the DNA in its helical state.
TMV is a rod-shaped virus which consists of single-stranded RNA and 2130 capsomeres or protein subunits arranged in a hollow right-handed helix.
PSTV (Potato Spindle Tuber Viroid) is an infectious agent of plants which consists of single-stranded closed circular RNA which is not associated with any protein.
Caulimo virus or Cauliflower Mosaic Virus is the first plant virus to be identified with DNA as a genetic material instead of RNA. The virus has the genetic material packed inside the icosahedral head made up of 420 protein subunits.
Thus, only PSTV is not having its genetic material associated with proteins.
So, the correct answer is C.

Tailed bacteriophages contain a common origin as well as represent an order with three families which are named as Caudovirales. The structure of their tail is only one of its kind. Tailed phages have a sequence of high-level taxonomic properties. They demonstrate several facultative appearances that are exclusive or unusual in viruses like, tail appendages and atypical bases.