Botany · Class 12 Science
Ch 14Viruses — Class 12 Botany, concept-first.
The existence of viruses first came to light through a puzzle involving diseased tobacco plants. In 1892, Dmitri Ivanowsky found that sap taken from tobacco plants showing mosaic disease remained infectious even after it had been passed through a fine porcelain filter known to trap ordinary bacteria - implying that wha…
Key concepts
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Discovery and Nature of Viruses
Viruses were discovered through a series of investigations into diseased tobacco plants. In 1892, Dmitri Ivanowsky found that the infectious sap of diseased tobacco plants passed straight through a fine porcelain filter…
Most relevant Q&A
Chapter contents
The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.
Discovery
The existence of viruses first came to light through a puzzle involving diseased tobacco plants. In 1892, Dmitri Ivanowsky found that sap taken from tobacco plants showing mosaic disease remained infe…
Classification of Viruses
Because viruses do not fit neatly into the schemes used to classify cellular organisms, a dedicated body called the International Committee on Taxonomy of Viruses (ICTV) was set up to standardise how…
Structure of Viruses
Chemically, a virus particle (or virion) is built from just two essential components: a core of nucleic acid, which carries the virus's genetic information, and a surrounding protein coat called the c…
Multiplication of Bacteriophages - The Lysogenic Cycle
Bacteriophages multiply inside a host bacterium by one of two alternative routes, the lytic cycle and the lysogenic cycle, both of which begin the same way: the phage attaches to the surface of a susc…
Viral Diseases in Plants
Viruses are responsible for a range of diseases in cultivated plants, and the very first virus ever discovered, the Tobacco Mosaic Virus, is itself the cause of one such disease: tobacco mosaic diseas…
Viral Diseases in Humans
21 QViruses also cause a wide range of diseases in humans, and the way medicine deals with viral disease is fundamentally different from the way it deals with bacterial disease, because a virus depends en…
+−Very Short Answer Questions9 questions
- Q1Distinguish between the living and non-living characters of viruses.Free
- Q2What is the shape of the T4 bacteriophage, and what is its genetic material?Free
- Q3What are virulent phages? Give an example.Free
- Q4What is lysozyme, and what is its function in the viral life cycle?Preview
- Q5Define lysis and burst size.Preview
- Q6What is a prophage?Preview
- Q7What are temperate phages? Give an example.Preview
- Q8Distinguish between virulent phages and temperate phages.Preview
- Q9What is the shape of the Tobacco Mosaic Virus (TMV), and what is its genetic material?Preview
+−Short Answer Questions8 questions
- Q1What is the ICTV, and how are viruses named?Free
- Q2Describe the chemical structure of viruses.Free
- Q3What is meant by the symmetry of a virus?Free
- Q4Describe the structure of the Tobacco Mosaic Virus (TMV).Preview
- Q5Describe the structure of a T-even bacteriophage.Preview
- Q6Describe the lytic cycle of a bacteriophage.Preview
- Q7What role do temperate phages play in transduction?Preview
- Q8Distinguish between the lytic cycle and the lysogenic cycle.Preview
+−Long Answer Questions2 questions
Sample & Board Papers
Sample papers and previous-year board questions for this subject.
+−Show 7 questionsHide questions7 questions
- Q1Explain the structure of T-even bacteriophages.Preview
- Q2Explain the structure of T-even bacteriophages.Preview
- Q3What is the shape of T4 phage? What is its genetic material?Preview
- Q4Explain the structure of T-even bacteriophages.Preview
- Q5What is ICTV? How are viruses named?Preview
- Q6What is the shape of TMV? What is its genetic material?Preview
- Q7What is ICTV? How are viruses named?Preview