what are the basic charatcteristics of viruses?

Answer 1

All viruses have at least two components: a nucleic acid core, and a protein capsid.

The nucleic acid core is either DNA or RNA, depending on the species of virus. Viruses typically have very small genomes - the smallest code for only four proteins, and the largest code for only a hundred or so. Unlike many cellular organisms, a viral genome is usually very compact with little wastage. While 99% of human DNA codes for nothing, some viruses not only have virtually no waste but use sections of their nucleic acids multiple times or for different things depending on the direction its read.

The capsid is a protective envelope that not only shields the nucleic acid material when it's outside of a cell, but also can provide specificity so it is only introduced into cells that it can take over. The simplest capsids are made up of just a few protiens and assemble themselves automatically when a bunch of them are produced by a cell. The more complex capsids look like complicated machines or simplified insects.

Some viruses carry along other things as well. Some can hijack a portion of a cell's mebranes for their own use and protection inside a capsid. Some bring along a variety of enzymes to help kickstart their control of a cell (reverse transcriptase is a popular one so RNA viruses can write themselves permanently into your DNA). And as you might imagine, the ones that haul along more stuff can accomplish different tasks at the expense of having to make it all again for new viruses.

How they operate can be pretty varied. Some viruses will enter a host cell and not really interfere with its normal processes but just tack their own tasks onto the list of things the cell is already doing. Some viruses are equipped to stop a cell from performing other tasks so its needs are the only ones being met. Some viruses replicate until the host cell dies, while others just trickle out viral particles indefinitely without killing the host. And some perticularly insidious viruses simply travel along with the host cell and wait... replicating as it replicates, and only taking over when the host cell seems threatened.

Outside of a host, viruses have proven to be about as hardy as an inorganic chemical. And since a viral particle isn't really DOING anything, it has no need of energy or nutrients. Viruses have been found that are still able to infect cells after thousands of years of waiting (it is thought that this is the source of the 'mummy's curse' in Egyptian tombs). Only bacterial endospores can hope to compete in terms of resilience. Viral particles are so inert, in fact, that many biologists consider them to not even be alive.

Yet their simplicity lends them to use by biologists. This remains one of the most popular ways of introducing new genes into adult organisms (called sometimes recombinant DNA therapy) - a biologist assembles an RNA version of the DNA he wants a patient to have, packs it in a viral coat with some reverse transcriptase, and injects a patient with it. Because it can't reproduce itself like a real virus, it just ends up jamming the new segment of DNA into an adult cell and then being digested. This has it's own drawbacks, though... because the new segment is put in pretty much randomly, it's hard to control exactly which cells get it and make sure they don't have important DNA sequences messed up by the new one.

All in all virology can be a fascinating field. Hope that helps!

Answer 2

basics: they ultramicroscopical biological particules( messured in nanometers), only capable to be seen using an electron microscope.
They all have a capside, an external proteic structure that envolves de inner DNA viral molecule . some viruses have a RNA molecule( i.e.: all the retroviruses, HIV, FIV(for feline) FeLeV( feline leucemia virus)), and also sometimes small structural proteins and enzimes. they always need bacterial or eucariothic cells to replicate. They enter the cell by the plasmatic membrane, most of the time attaching to it by specific proteic receptors. Once they enter, the capside is ussualy digested by lisosomic enzimes and then the DNA/RNA molecule is released, it enters the nucleus and attaches the DNA of the host to replicate, eventually kill the cell by excesive replication of viral particles in the citoplasm, and then spread to other cells. Some viruses only let the DNA molecule enter, sort of ¨inyecting¨the material into the cell.c The infecting viral particles ussually do not survive envornmental conditions;never the less, they are exceptions: CPV( canine parvovirus, it can last up to 2 years on humid and dirty soil, asnd resists some desinfectants). Some viruses replicate in the citoplasm, some in the nucleus. Sometimes you can see evidence of replication with an optical microscope: using rutine histological stain or even inmunehistochemical( inmunefluorescence), one can evidence small dots in the citoplasm/nucelus called ¨inclusion bodies¨.

Answer 3

Hi:

Viruses are basically a nucleic acid (ss/ ds DNA or RNA) surrounded by a protein coat. Some have a lipid coat, like the Inoviridae family of bacteriophages. They lack a cellular organization.
Viruses form a link between the world of the living and that of the non-living. This is cos they can be crystalized like non-living proteins or salts and they remain dormant, first demonstrated by Stanley with Tobacco Mosaic virus. But when you introduce the virus crystals to a host cell, they regain infectivity and, like live infectious agents, they can cause an infection.

They are wholly parasites and depend completely on their host cells for all their nutritional and replicative needs.

Hope this helps.
Cheers!

Answer 4

They are not technically a cell. They are strands of DNA or RNA that invade a host cell and take over the components of that cell and force it to replicate more virus genetic material.

Answer 5

Why did God create viruses?