Living Beings || Virus || DNA || RNA || Viruses
Ans: The branch of microbiological science which deals with the study of virus is called virology.
2. What is the size of virus?
Ans: The size of virus ranges from 25nm to 250nm.
3. What is meant by DNA virus? Give examples of it.
Ans: The virus which contains deoxyribonucleic acid as genetic material is called DNA virus. Example: Small poxvirus, Bacteriophases.
4. What do you mean by host specificity?
Ans: The special property of a parasite due to which it infects only a particular type of a host cell is called host specificity.
5. What is capsid? What is it made of?
Ans: The protein coat that encloses the nucleic acid of virus is known as capsid. Capsid is made up of smaller protein units called capsomeres.
6. What does RNA virus mean? Write the full form of DNA and RNA.
Ans: The virus which conatins ribonucleic acid as a genetic material is called RNA virus.
DNA = Deoxyribonucleic Acid
RNA = Ribonucleic Acid
7. Why are viruses called host specific?
Ans: The virus are called host specific because they attack only a particular type of host or a particular type of tissue. In general, viruses that attack a particular type of host do not attack other types of hosts.
8. What is meant by vector of virus?
Ans: The animals or insect which transmit the virus from infected plant to healthy plant is called vector of virus.
9. Write down the types of viruses on the basis of host.
Ans: There are three types of viruses on the basis of host. They are as follows;
i) Plant virus – For example: TMV, CMV, etc.
ii) Animal virus – For example: Retro virus, Rhino virus, etc
iii) Bacteriophases – For example: T-phages
iii. Both have well organized nucleus.
Ans: The following are the living characteristics of virus;
i. They can grow and multiply with the host cell.
ii. They have genetic material, DNA or RNA.
iii. They respond to chemicals, light, temperature, etc.
iv. They show mutation.
v. They are capable of spreading different diseases.
11. Write down the non-living characteristics of virus.
Ans: The bob-living characteristics of virus are as follows:
i. Viruses lack true cell structure.
ii. They do not have synthesized proteins.
iii. Some viruses can be crystallized like a chemical substance. For example: TMV.
iv. They do not respire.
12. Why viruses are called obligatory parasites?
Ans: Viruses are called obligatory parasites because they cannot multiply outside the body, but multiply within the cell of living body.
13. Why viruses cannot be cultured in artificial media?
Ans: Viruses cannot be cultured in an artificial medium because they are host specific for multiplication.
14. Virus is kept in the boarderline of living and non-living things. Give reason.
Ans: All viruses are totally parasitic and have like living organisms inside the living host cell, while they are quite inactive and seem to be dead out of the host cell. Viruses can be isolated, purified and crystallized like non-living things. So, the viruses are called boarderline of living and non-living things.
15. Virus is non-living but becomes living when it comes into contact with living matter. Give reason.
Ans: Viruses are visible only under the electron microscope. They can pass through the cell membranes. They cannot grow outside living cells and therefore they cannot be cultured in the laboratories. They can reproduce only inside the living cell of living host. So, virus becomes living when it comes to contact with living matter.
16. Viruses are called agent of the diseases. Give reason.
Ans: Viruses cause a wide range of diseases among living organisms. A few hundred plant diseases caused by viruses are recorded so far. For example, mosaic disease cauli, tobacco, mustard, cabbage, etc. Similarly, diseases caused by virus in human include AIDs, Mumps, Rabies, Measles, Chicken Pox, etc. So, viruses are called agent of the diseases.
17. What is the meaning of ‘VIRUS’ in Latinelanguage?
Ans: In Latine language, virus means venon (poisonous liquid).
18. In what respect do the virus resemble with bacteria?
Ans: The resemblance of viruses with bacteria are;
i. Both are microscopic organisms.
ii. Both are pathogens which cause different diseases to organisms.
iii. Both have well organized nucleus.