Tag: #RNA

VIRUS AND ITS TRANSMISSION

WHAT IS A VIRUS?????
A virus is referred as an infectious agent that can only replicate inside the living cells of an organism i.e. a virus is something which can not at all grow or replicate by its own. It always needs a living cell for its replication process. It is a microorganism which cannot be seen by naked eyes and can infect any life form. It can be infectious for humans, plants and even for other microorganisms like bacteria and archea. Viruses infecting bacteria are known as bacteriophage. Viruses are not restricted to a place and they can be found everywhere at every place of ecosystem whether land, or water or in air. They can cause various infections including air-borne, water-borne or even food-borne. The science dealing with the study of viruses is known as Virology and it is a branch of microbiology. A complete virus particle ranges in size from about 10-400nm in its diameter.
Viruses are near to dead when outside the living cell but once entered any living cell of an organism, they are forced to replicate using the life machinery of that particular organism and thus they produce thousands of their multiple copies and in this way infect the organism. Outside the living cells they are present in the free, independent form which may also be known as a virion.
There are 3 main parts in the structure of a virus i.e. –

  1. Genetic core which is also known as nucleic acid core containing all the genetic material whether DNA or RNA, but not both. It is known as genome.
  2. A protein coat, which is also known as capsid which surrounds the genome of a virus particle.
  3. An envelope which is made of lipid. It is an external coat surrounding the genome as well as capsid.

VIRUS TRANSMISSION
Transmission of virus particles is important for them to survive because as discussed above they can only replicate themselves inside a host living organism. The virus transmits from one organism to another in order to survive, reproduce and continue their species. The effectiveness of the transmission of viral particle depends on 2 main factors i.e. the concentration of virus and its route of transmission. More concentration of virus leads to more transmission.
There are several ways by which a virus particle may get transmitted from one organism to another.

  1. Blood – Virus particles can get transmitted through the blood. The one way is direct viral infection in blood and the other way is by arthropods like dengue or malaria is transmitted. Arthropods bite one organism and collect viral particles from them and then when they bite other organism, the same viral particles are being transmitted to the next organism and this way transmission and infection occurs. Another way is direct viral infection in blood which can be via direct infected blood exposure to a healthy individual. It may be transmitted via sexual contacts with infected person like HIV is transmitted.
  2. Saliva – It is the most commonly seen in kissing the infected individual. The saliva contains the viral particles and thus they are transmitted to healthy individual.
  3. Respiratory secretions – If any infected individual sneezes, or coughs or in any other way its respiratory secretions come in contact with the healthy individual, he may get infected by the same. It may also occur by singing or even breathing.
  4. Feces – This is not a very common method in developed countries but can infect those who do not take sanitary actions after using toilets. The virus particles secreted in feces can infect other healthy individuals if they come in contact with them.

The origin of life-RNA WORLD?????

The origin of life depends on the singe question – How did early cells could have arisen?
Modern cells consist at a minimum of plasma membrane enclosing water in which numerous chemicals are dissolved and sub cellular structures float. It was thus believed that the first self-replicating entity was much simpler than even the most primitive modern living cells. Before there was life, and yes, Earth was a different place: completely hot and anoxic, with an atmosphere which was completely rich in gases such as hydrogen, methane, carbon dioxide, nitrogen, and ammonia. Earth’s surface was like a pre biotic soup in which chemicals reacted with one another, randomly “testing” the usefulness of the reaction and the stability of the resulting molecules. Some reactions released energy and would eventually become the basis of modern cellular metabolism. Other reactions which occurred created molecules that could function as catalysts, some aggregated with other molecules to form the predecessors of modern cell structures, and others were able to replicate and act as units of hereditary information.
Proteins have two major roles in modern cells – structural and objective.
Catalytic proteins are called enzymes, in cells. Thus enzymes act as the workhorses of the cell. DNA stores hereditary information and can be replicated to pass the information on to the next generation. RNA is involved in converting the information stored in DNA into proteins. Proteins can do cellular work, but their synthesis is dependent on their proteins and RNA, and information stored in DNA. DNA can’t do cellular work. It’s only work is to store genetic information and it is involved in its own replication process which is a process that requires proteins. RNA is synthesized using DNA as the template and proteins as the catalysts for the reaction.
Based on these considerations, it seemed to evolutionary biologists that at some time in the evolution of life there must have been a single molecule that could do both cellular work and replicate itself. A possible solution to the nature of this molecule was suggested in 1981 when Thomas Cech discovered an RNA molecule in the protest Tetrahymena that could cut out an internal section of itself and slice the remaining sections back together. Since then, other catalytic RNA molecules have been discovered, including an RNA found in ribosomes that is responsible for forming peptide bonds – the bonds that hold together amino acids, the building blocks of proteins. Catalytic RNA molecules are now called ribozymes.
The discovery of ribozymes suggested the possibility that RNA at some time had the ability to catalyze its own replication, using itself as the template. In 1986, a term was coined – RNA WORLD to describe a precellular stage in the evolution of life in which RNA was capable of storing, copying, and expressing genetic information. Also it catalyzes other cellular chemical reactions. This important evolutionary step is easier to imagine than other events in the origin cellular life forms because it is well known that lipids, major structural components of the membranes of modern organisms, form liposomes which are bounded by a lipid layer.