Genetic material replication and protein synthesis using machinery of the host. Replication mode: lytic and lysogenic cycle. The difference is given in points which is more convinient Do viroids respond to thermotherapy to eliminate them from infected plants? In other words, can infected plants treated with thermotherapy become clean and viroid free? I wish all professors are as simple as this I wish all professors are as easy as simple as this..
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Facebook Twitter. Virus is an obligate intracellular parasite which can reproduce only by invading and taking over other cells as they lack the cellular machinery for self reproduction. Viroids are subviral, smallest known agents of infectious disease. The term viroid was coined by T. Diener to describe the causal agent of the potato spindle tuber disease PSTV.
There are some 25 viroids which vary in nucleotide sequence. Viroids are spread by plant propagation cuttings and tubers through seeds and by manual mishandling with contaminated implements. Virus vs Viroid. It is a nucleoprotein particle.
A protein covering or coat called capsid is present around the genetic material. Historically, the idea of an infectious agent that did not use nucleic acids was considered impossible, but pioneering work by Nobel Prize-winning biologist Stanley Prusiner has convinced the majority of biologists that such agents do indeed exist.
The disease was spread by the consumption of meat, nervous tissue, or internal organs between members of the same species. Kuru, native to humans in Papua New Guinea, was spread from human to human via ritualistic cannibalism. BSE, originally detected in the United Kingdom, spread between cattle by the practice of including cattle nervous tissue in feed for other cattle. Individuals with kuru and BSE show symptoms of loss of motor control and unusual behaviors, such as uncontrolled bursts of laughter with kuru, followed by death.
Kuru was controlled by inducing the population to abandon its ritualistic cannibalism. On the other hand, BSE was initially thought to affect only cattle. Later on in the outbreak, however, it was shown that a similar encephalopathy in humans known as variant Creutzfeldt-Jakob disease CJD could be acquired from eating beef from animals with BSE, sparking bans by various countries on the importation of British beef and causing considerable economic damage to the British beef industry.
BSE still exists in various areas. Although a rare disease, individuals that acquire CJD are difficult to treat. The disease spreads from human to human by blood, so many countries have banned blood donation from regions associated with BSE. The cause of spongiform encephalopathies, such as kuru and BSE, is an infectious structural variant of a normal cellular protein called PrP prion protein. It is this variant that constitutes the prion particle.
This leads to an exponential increase of the PrP sc protein, which aggregates. Moreover, the virus consists of a protein coat known as the capsid while viroids lack a protein coat. Viruses and viroids are two forms of infectious particles, which can reproduce exclusively inside a host cell. What is a Virus — Definition, Structure, Importance 2.
What are Viroids — Definition, Structure, Importance 3. A virus is a non-living, small, infectious agent, which can only replicate inside a host cell. Generally, viruses are not equipped with the cellular mechanisms required by the replication including DNA replication and protein synthesis. Therefore, they have to depend on a host cell to replicate their nucleic acids and to synthesize their protein coat.
Hence, viruses are obligate, intracellular parasites, which invade cells, causing diseases. Figure 1: Structure of a Virus.
Furthermore, outside the host cells, viruses occur as independent particles known as virions. Therefore, based on the type of nucleic acids present in the genome, we can classify viruses as DNA viruses and RNA viruses.
Moreover, a virion consists of a protein coat, surrounding the genetic material known as the capsid. Thus, based on the shape of the capsid, viruses are classified as helical, icosahedral, prolate, and complex viruses. Some of the virions consist of an envelope made up of lipids surrounding the capsid.
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