Test: Virus - 1a - NEET MCQ

• Potatoes may be infected with many different viruses that can reduce tuber quality and yield.
• Mosaic virus of potatoes is one such disease that actually has multiple strains.
• The potato mosaic virus is divided into three categories. Symptoms of the different mosaic viruses of potatoes may be similar, so the actual type usually can’t be identified by symptoms alone and is often just referred to as mosaic virus in potatoes.

Hence, the correct option is C.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Tobacco mosaic virus (TMV) is a positive-sense single-stranded RNA virus.
• The infection causes characteristic patterns, such as "mosaic"-like mottling and discoloration on the leaves (hence the name).

Hence, the correct option is A.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

Mumps is caused 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.

Hence, the correct option is B.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses are smaller when compared to bacterium.
• Viruses that can infect bacterium are called bacteriophages.
• Bacteriophages contain double stranded DNA (Deoxy ribonucleic acid).

Hence, the correct option is A.

NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• The Potato Spindle Tuber Viroid ("PSTVd"), the first viroid to be identified, is a small, circular RNA molecule closely related to the Chrysanthemum stunt viroid.
• Since it is a viroid and does not contain protein coat and contains single-stranded RNA, hence, option A is correct and other options are wrong.

Hence, the correct option is A.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses do not carry out metabolic processes. Most notably, viruses differ from living organisms in that they cannot generate ATP.
• They do not possess ribosomes and cannot independently form proteins from molecules of messenger RNA.

Hence, the correct option is A.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Rabies lyssavirus, formerly Rabies virus, is a neurotropic virus that causes rabies in humans and animals. These viruses are enveloped and have a single-stranded RNA genome with negative sense.
• Rabies transmission can occur through the saliva of animals and less commonly through contact with human saliva.

Hence, the correct option is A.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• A capsid is the protein shell of a virus.
• It consists of several oligomeric structural subunits made of protein called protomers.

Hence, the correct option is C.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

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

Hence, the correct option is A.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses are an example of obligate parasites.
• Viruses can’t perform any of their metabolic activities when they are outside a living host.
• As soon as they enter a living host they replicate and perform their metabolic activities. Therefore, they are an example of obligate parasites.

Hence, the correct option is A
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 7.

• Viruses contain either RNA or DNA whereas viroids contain only free RNA. 
• Viruses contain protein coat whereas viroids don’t contain protein coat. 
• Viruses are found in bacteria, animals and plants but viroids are found only in plants.

Hence, the correct option is A.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• φ x 174 bacteriophage - ss DNA
• Mycophage - ds RNA
• pox virus - ds DNA
• Poliovirus - ssRNA

Genome of the ϕ × 174 bacteriophage is a single stranded DNA. It contains 11 genes. It infects Escherichia coli.

Genome of the mycophage is double stranded RNA. It infects mycobacteria.

Genome of pox virus is a double stranded DNA. It causes smallpox.

Genome of polio virus is single stranded RNA. It is a member virus of Enterovirus C. It causes polio.

Hence, the correct option is D.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Mumps, smallpox, herpes and influenza are caused due to viruses.
• Whereas, T.O.Diener in 1971 discovered that potato spindle tuber disease is caused by a set of pathogens that are similar to viruses and named them as viroids.

Hence, the correct option is D.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses can’t perform any of the metabolic activities when outside a living host. So, they are non-living organisms.
• Viruses don’t even consist of a cell and are so acellular.
• They are in fact smaller than that of a bacterium and can even infect them.

Hence, the correct option is C.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viroids are the smallest infectious pathogens known.
• They are composed solely of a short strand of circular, single-stranded RNA that has no protein coating.

Hence, the correct option is D.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Lichens exist in symbiotic associations with algae and fungi.
• The algal and fungal components in Lichens are known as Phycobiant and Mycobiant respectively.

Hence, the correct option is A
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Virus, 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 “venom” or “poisonous fluid.”

Hence, the correct option is D.
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses are ultramicroscopic disease-producing organisms. They have two fundamental characteristics of the 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.

Hence, the correct option is D
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2

• The co-existence of algae with fungus is called lichens.
• Lichens are the best examples of the symbiotic association.
• They are also good indicators of pollution as they don’t grow in polluted regions.

Hence, the correct option is B
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses are made up of nucleic acid, which is DNA/RNA with protein. Cell membrane, protoplasm, ribosomes, etc., are absent. Since it lacks metabolism, it lacks enzymes.
• Fungi, algae, and cyanobacteria, on the other hand, have a variety of enzymes as it is made up of the cell.

Hence, the correct option is B
NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• 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.

Hence, the correct option is D
NCERT Reference: Page no. 25 of chapter “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viruses don’t contain cell and instead have genetic material made of nucleic acids and a protein sheath covering it which is made of proteins.
• This protein sheath is called capsid and is made of basic units called capsomeres.

Hence, the correct option is B.
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

A virus is a small infectious agent that  replicates only inside the living cells of other organisms.

• Option A: Viruses can undergo replication by lytic and lysogenic cycles.
• Option B: The feature of viruses to perform viral genetic change in their own genome is a process of virus mutation.
• Option C: The energy production and liberation process are absent in viruses, as this process is not required by viruses. 

Hence, the correct option is C
NCERT Reference: Page no. 25 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• Viroids are the smallest infectious pathogens known.
• They are composed solely of a short strand of circular, single- stranded RNA that does not encode a protein. This viroid is called Potato Spindle Tuber Viroid (PSTV).

Hence, the correct option is C
NCERT Reference: Page no. 27 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.

• The outer protein coat of a virus is known as the capsid.
• It consists of several oligomeric structural subunits made of a protein called protomers which cover the nucleic acid which is present in the virus and protects it when virus inserts itself into the host.
• The capsid proteins also help the virus attach and penetrate the host cells thereby infecting the host.

Hence, the correct option is B.

NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2.