Biological Classification Test 4

• 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.
• 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.

• 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).

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.

• AIDS(acquired immunodeficiency syndrome) is caused by the HIV virus. It breaks down the body immune system, leaving the patient vulnerable to a host of life-threatening opportunistic infections.
• T-helper cells play an important role in adaptive immunity. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
• HIV destroys(CD4+ cells) T-helper lymphocytes cells.They're responsible for keeping you healthy from common diseases and infections. As HIV gradually weakens your natural defences, signs and symptoms will occur.
• Hence HIV attacks T-helper cells. Hence AIDS is caused by HIV that principally infects T-4 helper lymphocytes.

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 contains single-stranded RNA, option A is correct and other options are wrong.

• 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

• 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.

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

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

Interferon act as cell mediated immunity when one pathogen attacks the immune system it gets treated and set as memory. So when the same pathogen attacks again interferon act against it.

Apical meristem is not infected by the virus because the rate of division of meristematic cell is higher than the rate of multiplication of virus and viruses are unable to invade newly formed meristematic cells.

A complete virus particle, known as a virion, consists of nucleic acid surrounded by a protective coat of protein called a capsid.

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.

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

Waksman is credited with coining the term antibiotics, to describe antibacterials derived from other living organisms.

• 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 so acellular.
• They are in fact smaller than that of a bacterium and can even infect them.

• Cauliflower mosaic virus (CaMV) is a member of the genus Caulimovirus, one of the six genera in the Caulimoviridae family, which are pararetroviruses that infect plants.
• Pararetroviruses replicate through reverse transcription just like retroviruses, but the viral particles contain DNA  (double Strand) instead of RNA.

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.

Myxovirus, any of a group of viruses of the families Orthomyxoviridae (agents of influenza) and Paramyxoviridae, members of which can cause the common cold, mumps, and measles in humans, canine distemper, rinderpest in cattle, and Newcastle disease in fowl.

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 “slimy liquid” or “poison.”

The majority of mycoviruses have double-stranded RNA  genomes and isometric particles, but approximately 30% have positive-sense, single-stranded RNA  genomes.

• Viruses are considered neither prokaryotes nor eukaryotes because they lack the characteristics of living things, except the ability to replicate which they accomplish only in living cells.
• Akaryota includes organisms having no cells. All viruses are placed under akaryota.

Hence, option C is correct.

A virus is a unit of infectious genetic material, generally smaller than bacteria. Viruses are considered to be both living and non-living.

• They are considered to be living as they possess a protein coat as a protective covering, DNA as the genetic material, etc.
• They are said to be non-living as they can be crystallized and they survive for billions of years.

• In virology, temperate refers to the ability of some bacteriophages (notably coliphage λ) to display a lysogenic life cycle.
• Many (but not all) temperate phages can integrate their genomes into their host bacterium's chromosome, together becoming a lysogen as the phage genome becomes a prophage.

• 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.

• 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.

• 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 the virus does not take place through vegetative propagation.

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, option C is correct.

• 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 as Potato Spindle Tuber Viroid (PSTV).

• Creutzfeldt-Jakob disease (CJD) is caused by an abnormal infectious protein in the brain called a prion.
• Proteins are molecules made up of amino acids that help the cells in our body function. They begin as a string of amino acids that then fold themselves into a 3-dimensional shape.

Creutzfeldt-Jakob disease: