Students can go through AP Inter 2nd Year Botany Notes 8th Lesson Viruses will help students in revising the entire concepts quickly.
AP Inter 2nd Year Botany Notes 8th Lesson Viruses
→ Viruses are unique group of biological entities, those can infect Bacteria, Algae, Fungi, Protozoa, Plants and Animals.
→ Viruses are not composed of cells and cannot be seen under a light microscope.
→ The study of viruses is known as Virology.
→ Tobacco Mosaic virus was discovered by Iwanowski.
→ Virus particles are called virions.
→ A virus particle contains a protein coat inside with either DNA or RNA.
→ Viruses maintain genetic continuity through multiplication and undergo mutations. Viruses are best described as infectious particles.
→ Viruses are obligate intracellular parasites i.e., they cannot multiply unless they invade a specific host cell.
→ Stanley was awarded Nobel Prize for the crystallization of TMV. .
→ Fraenkel, Contrat confirmed that the genetic material of the TMV is RNA.
→ International Committee on Taxonomy of Viruses [ICTV] regulates the norms of classification and nomenclature of viruses.
→ The ICTV scheme has 3 hierarchial levels, – The Family, Genus and Species.
→ According to ICTV the virus that causes Acquired Immune Deficiency Syndrome (AIDS) is classified as family :- Retroviridae, Genus – Lentivirus, Species Human Immune deficiency Virus [HIV].
→ Viruses are made up nucleic acid [either DNA or RNA] and protein coat called capsid.
→ TMV is a rod-shaped virus, have RNA as genetic material and capsid with 2130 capsomeres.
→ Bacteriophages are tadpole-shaped viruses.
→ T-even phages that attack the bacterium E.Coli cause lysis of the cells and are called virulent phages. They show lytic cycle.
→ The number of newly synthesized phage particles released from a single cell is referred to as the burst size (50-200).
→ The phage DNA gets integrated into the bacterial chromosome, becomes part of it and remains inactive are called temperate phages. They show lysogenic cycle.
→ Viral diseases are chlorosis [peach yellow disease] Mosaic [TMV], Vein clearing [bhendi vc], malformation [swollen shoot of cocoa] and breaking of flowers [Tulip Mosaic disease].
→ Unusually a tiny fragment of nucleic acid with 300-400 nucleotides and without a protein coat called viroid, can cause diseases in tomato, potato, cucumber etc.
→ Chronic hepatitis-B may lead to cancer called Oncoviruses.
→ Some proteinaceous infectious.particles called prions cause some serious animal diseases like mad cow disease (Bovine Spongiform Encephalitis) in cows and scrapie disease in sheep.
→ Viruses are very small, infectious, obligate intracellular parasites.
→ Viruses are known to infect every type of cell including bacteria, algae,fungi,plants, animals.
→ Viruses are not composed of cells and cannot be seen under a light Microscope.
→ Study of viruses is called virology.
→ The complete particle of virus is called viron.
→ A virus particle contains single type of nucleic acid.
→ Its genome is a single standard circular DNA or RNA.
→ They have a nucleic acid core protected by a protein capsid.
→ Viruses donot exhibit most of the life processes of a cell.
→ But they maintain genetic continuity through multiplication and they under go mutations.
→ Viruses multiply in host cells which they attack.
→ Virulent phages follow lytic cycle of replication.
→ Temperate phages follow lysogenic cycle of replication.
→ In this process, viruses cause several human, plant and animal diseases.
→ The viruses which cause Cancer are called Oncogenic viruses.
→ Viruses that attack bacteria are called bacteriophages.
→ Infectious agents simpler than viruses are called Prions.
→ Prions are proteinaceous infectious agents.
→ Prions cause diseases like mad cow disease in cows.
→ The viral enzyme which dissolves the plasma membrane of host cell is called lysozyme. [IPE]
→ TMV stands for Tobacco Mosaic Virus. The shape of TMV is rod. [IPE]
→ The genetic material of TMV is single stranded RNA consisting of 6500 nucleotides. [IPE]