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Questions and Answers
What does the term 'virus' mean in Latin?
What does the term 'virus' mean in Latin?
poison
What are the two main components of a virion?
What are the two main components of a virion?
Genetic material and protein coat
What is the name given to the protein coat that surrounds the nucleic acid in a virus?
What is the name given to the protein coat that surrounds the nucleic acid in a virus?
capsid
What is the term for the complete entity of nucleic acid packaged inside the protein coat?
What is the term for the complete entity of nucleic acid packaged inside the protein coat?
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What is the name of the field that studies viruses?
What is the name of the field that studies viruses?
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Which of the following are considered the main characteristics used for virus classification?
Which of the following are considered the main characteristics used for virus classification?
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What are the two main classification schemes used for viruses?
What are the two main classification schemes used for viruses?
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Which of these is a defining feature of the ICTV classification system?
Which of these is a defining feature of the ICTV classification system?
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What is the basis of the Baltimore classification system?
What is the basis of the Baltimore classification system?
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How many groups are viruses categorized into within the Baltimore classification system?
How many groups are viruses categorized into within the Baltimore classification system?
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DNA viruses typically replicate inside the nucleus of the cell.
DNA viruses typically replicate inside the nucleus of the cell.
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RNA viruses replicate in the cytoplasm of the cell.
RNA viruses replicate in the cytoplasm of the cell.
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RNA viruses tend to mutate faster than DNA viruses.
RNA viruses tend to mutate faster than DNA viruses.
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What are the four main stages of viral replication?
What are the four main stages of viral replication?
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What is the name of the process by which a virus binds to a specific receptor on a host cell?
What is the name of the process by which a virus binds to a specific receptor on a host cell?
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What process follows attachment, where the virus enters the host cell?
What process follows attachment, where the virus enters the host cell?
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What is the name of the stage where the virus uses host cell machinery to produce new viral particles?
What is the name of the stage where the virus uses host cell machinery to produce new viral particles?
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What are the two categories of proteins produced during the synthesis stage?
What are the two categories of proteins produced during the synthesis stage?
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What are the two main processes involved in viral particle formation?
What are the two main processes involved in viral particle formation?
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What are the two main ways viruses can be released from a host cell?
What are the two main ways viruses can be released from a host cell?
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What are the two main life cycles of a bacteriophage?
What are the two main life cycles of a bacteriophage?
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Viroids are sub-viral pathogens that lack a protein coat.
Viroids are sub-viral pathogens that lack a protein coat.
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Prions are made entirely of protein and lack DNA or RNA.
Prions are made entirely of protein and lack DNA or RNA.
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What is the name of the protein that prions are derived from?
What is the name of the protein that prions are derived from?
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Study Notes
Course Information
- Subject: Biochemistry
- Paper: 03
- Module: 08
- Topic: Structure and Function of Biomolecules II (DNA and RNA Viruses)
Principal Investigators and Coordinators
- Principal Investigator: Dr. Sunil Kumar Khare, Professor, Department of Chemistry, IIT-Delhi
- Paper Coordinator and Content Writer: Dr. Sunil Kumar Khare, Professor, Department of Chemistry, IIT-Delhi & Prof. M.N. Gupta, Department of Biochemical Engineering and Biotechnology, IIT-Delhi
- Content Reviewer: Dr. Arun Goyal, Professor, Department of Biotechnology, Indian Institute of Technology Guwahati, North Guwahati, 781 039 Assam, India
Objectives
- Understand viruses and their classification
- Learn about DNA and RNA viruses
- Explore how viruses infect and replicate in a host
- Examine virus-like particles (e.g., viroids and prions)
Concept Map
- Viral Class: DNA Viruses and RNA Viruses
- Viral Genome: single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), single-stranded RNA (ssRNA), double-stranded RNA (dsRNA)
Description and Introduction
- Viruses are pseudo-living particles with some chemical similarities to living cells.
- They are contagious agents causing various deadly diseases (e.g., smallpox, influenza, yellow fever).
- Viruses are submicroscopic acellular entities composed of DNA or RNA with a protein coat.
- They are obligate intracellular parasites that replicate only within a suitable host.
- Viruses have a period outside the host cell, existing in an extra-cellular form.
- Viruses utilize the host's machinery for replication, transcription, and protein synthesis.
- Virology is the study of viruses.
History of Viruses
- Viral diseases have been known for a long time, even before the exact cause was known.
- Variolation or vaccination (inoculation with attenuated viruses) was popularized by Edward Jenner in 1798.
- Dmitri Ivanovski demonstrated that sap from infected plants, even after filtering out bacteria, could still cause infection, implying the existence of a filterable virus.
- Martinus Beijerinck discovered that a causative agent smaller than bacteria was responsible for the disease.
- Development of electron microscopy and other techniques enabled detailed observation.
Viral Structures
- Viruses come in various shapes and sizes (30-400 nm).
- Their structure includes a nucleic acid core (DNA or RNA) enclosed within a protein coat (capsid).
- Capsids are composed of repetitive protein subunits called capsomeres.
- Some viruses have an outer envelope derived from the host cell membrane.
- These structures (nucleocapsids) are mostly symmetrical in shape.
Viral Classification
- There are four types of virion structure: icosahedral, helical, enveloped, and complex.
- Various classification systems exist, such as the Baltimore classification (based on viral nucleic acid and replication strategies) using a system with seven classes of virus organisms.
- The International Committee on Taxonomy of Viruses (ICTV) defines species in terms of viral properties.
DNA and RNA Viruses
- DNA viruses replicate within the nucleus, generally using cellular enzymes, have a low mutation rate and often cause chronic infections.
- RNA viruses mostly replicate in the cytoplasm, with a high mutation rate. Their replication often involves unique enzymes and mechanisms.
Viroids and Prions
- Viroids are sub-viral pathogens that infect plants and are composed of small, naked RNA molecules.
- Prions are infectious agents composed solely of protein. They can cause neurological diseases by converting normal proteins to abnormal forms.
Viral Replication
- Viruses attach to host cells and penetrate them, releasing their genetic material.
- The virus's genetic material takes over the host cellular machinery.
- New viral components are synthesized, assembled, and released to infect other cells.
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Description
Test your understanding of the structure and function of DNA and RNA viruses in this quiz for Biochemistry Paper 03, Module 08. The quiz covers virus classification, infection mechanisms, and related concepts like viroids and prions. Challenge yourself to grasp the complexities of viral biology!
