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Viruses and Research Study Guide

🗻 Big Picture: A virus is a parasite formed by a small collection of genetic codes composed of either RNA or DNA. Let us delve into this interesting world of viruses and the research carried out on them.

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Introduction

Did you know that viruses are technically parasites? Viruses are unable to reproduce independently and thus require a living organism within which to replicate, often harming or killing their host in the process. Scientists have studied viruses in detail - a scientific discipline by itself, known as virology.


What are viruses?

virus

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A virus is an infective agent consisting of a nucleic acid surrounded by a protein coat that is too small to be seen through light microscopy and is unable to reproduce without a host cell. A great deal of research has been critical in helping us understand the core characteristics of a virus, which we'll briefly cover below.

  • The viral particle, or virion, contains has a single nucleic acid with either an RNA or DNA core.

  • DNA viruses replicate in the host cell's nucleus, while RNA viruses generally replicate in the cytoplasm.

  • Viruses are grouped into families based on the type of nucleic acid they have, the presence or absence of a viral envelope, and their mode of replication.

  • Single-stranded RNA viruses are classified further depending on whether they have positive or negative RNA.

  • Proteins or enzymes surround viruses and are essential to their initial replication.

  • Viruses that replicate within an animal, plant, or bacterial cell are referred to as obligate intracellular parasites.

There have been instances in the past when viruses have caused devastation to plants, animals, and humans.

  • Diseases like foot and mouth, polio, and smallpox are well-known examples of viruses that affect both humans and other animals.

  • Other viruses like tobacco mosaic and tomato spotted wilt have caused significant economic losses by affecting entire crops in both quality and yield.


How do viruses work?

Viruses cannot survive independently, and thus need an animal, plant, or bacterial host in order to replicate. They are often transmitted through contaminated food and water supplies, as well as through respiratory droplets released when an individual coughs or sneezes.

Viruses can enter their host via vertical or horizontal transmission, which are defined as:

  • Horizontal trasmission occurs when a virus spreads through individuals of the same generation.

  • Vertical transmission occurs when a virus spreads from mother to child.

Viruses can spread through direct or indirect transmission, which are defined as:

  • Direct transmission occurs with physical contact between an infected and an uninfected host.

  • Indirect transmission occurs when a virus is transmitted through contact with any contaminated object or material.


Ongoing Research and Viral Therapy

Since viruses are so great at integrating into the genome of a host cell, why not make use of them to alter genetic components of other non-viral cells? Virotherapy is an early but highly promising area of research involving the use of viruses to treat non-virus related illnesses. Viral vectors are utilized to carry specific genetic information/alterations to a sick cell in an attempt to reverse the damage, which has been used for cancer treatments, gene therapy, and immunotherapy.

Viviotherapy utilizes viruses to fight diseases in three ways:

  • Gene knockout: the removal of a disease causing-gene in the cell

  • Gene overexpression: the excessive expression of a required gene, the lack of which causes the disease in the first place

  • Apoptosis induction: the delivery of certain genes that can cause cell death. Some examples of how this process is used in therapy.

Examples of how viruses are used to fight disease include the following:

  • Phages have been found used as an alternative to antibiotics, which appears promising in fighting multi-drug resistant strains of bacteria.

  • Oncolytic viruses lyse and kill cancer cells. The biggest challenge with this form of therapy is ensuring that that non-cancerous cells are not targeted in the process.

  • Adenovirus vector (AVV) therapy involves the insertion of a gene into the viral vector which is used to introduce the modified DNA into the diseased human cell.

virus

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💡 Summary

  • A virus is an infective agent consisting of a nucleic acid surrounded by a protein coat that is too small to be seen through light microscopy and is unable to reproduce without a host cell.

  • Viruses can be passed on either vertically or horizontally, and are spread through both direct and indirect transmission.

  • Virotherapy is an area of research involving the use of viruses to treat non-virus related illnesses.

  • Viviotherapy techniques include gene knockout, gene overexpression, and apoptosis induction.


FAQs

1. Are viruses alive?

Short answer? No. When researchers first discovered viruses, they observed that they behave similarly to bacteria, which is why they were initially considered to be biologically alive. In 1930, however, it was demonstrated that the virion did not have the mechanism which necessary for metabolic functions, were thus classified as nonliving organisms.

2. What are the two types of virus transmission?

Horizontal transmission, which occurs when a virus is transmitted through individuals of the same generation, adn vertical transmission, in which a virus is passed on from mother to child.

3. Can viruses be helpful?

Yes. Viruses are used to fight nonviral diseases through gene knockout, gene overexpression, and apoptosis iduction, all of which are forms of viviotherapy.

We hope you enjoyed studying this lesson and learned something cool about Viruses and Research! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don't forget to download our App to experience our fun, VR classrooms - we promise, it makes studying much more fun! 😎

Sources

  1. Viruses in Research. https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/7.17/primary/lesson/viruses-in-research-and-medicine-bio/ Accessed 10 Dec, 2021.

  2. Viruses in Research and Medicine. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Introductory_Biology_(CK-12)/07%3A_Prokaryotes_and_Viruses/7.15%3A_Viruses_in_Research_and_Medicine Accessed 10 Dec, 2021.

  3. What is Virology? https://www.news-medical.net/health/What-is-Virology.aspx Accessed 10 Dec, 2021.