Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – , India

SBT/SBI/SGS011-CP2-01 Introduction Programmes and Courses  SEP –SBT011 -U2-CP2  SEP –SGS011 -U2-CP2

School of Science and Technology, Online Counseling Resource… Credits  Academic Inputs by Sonali Alkari Faculty YCMOU Nagpur Centre, Faculty LAD college P.G. D of Biotechnology Research officer Ankur Seeds Pvt Ltd

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives After studying this module, you should be able to:  Describe viruses  Discuss different types of viruses  Explain structure of viruses

School of Science and Technology, Online Counseling Resource…

Introduction:1  The smallest organisms called as microorganisms or microbes include the bacteria (prokaryotes), viruses, fungi and protoctists.  All these microorganisms are studied together for the practical reasons because the techniques used in their study are similar.  The Russian botanist D.I. Ivanovasky [1985] prepared an infectious extract from tobacco plant suffering from mosaic disease.  In 1898 Dutchman Beijerink coined the term “virus” (Latin for poision) to such infectious extract obtained from plant tissue.

School of Science and Technology, Online Counseling Resource… Introduction:2  Viruses are among the first biological structures to be studied when electron microscope was developed in 1930s.  A virus (from the latin virus meaning "toxin" or "poison"), is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell.  Each viral particle, or virion, consists of genetic material, DNA or RNA, within a protective protein coat called a Capsid.  The capsid shape varies from simple helical and icosahedral (polyhedral or near-spherical) forms, to more complex structures with tails or an envelop.

School of Science and Technology, Online Counseling Resource… Introduction:3  Viruses infect cellular life forms and are grouped into animal, plant and bacterial types, according to the type of host infected.  Viruses often damage or kill the cells that they infect, causing disease in infected organisms.  A few viruses stimulate cells to grow uncontrollably and produce cancers.  Although many infectious diseases, such as the common cold, are caused by viruses, there are no cures for these illnesses.  The difficulty in developing antiviral therapies stems from the large number of variant viruses that can cause the same disease, as well as the inability of drugs to disable a virus without disabling healthy cells.

School of Science and Technology, Online Counseling Resource… Characteristics :1 Viruse have the following characteristics.  They are the smallest living organisms  They do not have a cellular structure.  They can only reproduce by invading living cells.  Therefore they are all parasitic.  They are obligate endoparasities, meaning that they can only live parasitically inside other cells.

School of Science and Technology, Online Counseling Resource… Characteristics :2  They have a simple structure, consisting of a small piece of nucleic acid, either DNA or RNA, surrounded by a protein or lipoprotein.  They are on the boundary between what we regard as living and non-living.  Each type of virus will recognize and infect only certain types of cell.  Viruses are highly specific to their host.

School of Science and Technology, Online Counseling Resource… The Polio virus, left, once crippled millions. Courtesy of the MicrobeLibrary.org; © Jean-Yves Sgro, University of Wisconsin. The T4 bacteriophage, middle, is a virus that invades bacterial cells. Courtesy of the MicrobeLibrary.org; © Dennis Kunkel. Gold clusters bound to the knob protein of Adenovirus, right. Courtesy of Brookhaven National Laboratory. Viruses Polio virusT4 bacteriophageAdenovirus,

School of Science and Technology, Online Counseling Resource… Characteristics:3  Viruses are the smallest living organisms, ranging in size from about nm.  They cannot be seen with the light microscope and they pass through filters which retain bacteria.  On average they are about 50 times smaller than bacteria.  Often viruses reside in their host without causing any disease or symptom. Such latent viruses are undiscovered.

School of Science and Technology, Online Counseling Resource… Are Viruses Living?  This question is often posed.  If, to be defined as living, a structure must possess genetic material(DNA or RNA), and be capable of reproducing itself.  It to be noted that viruses are not capable of reproducing outside the host cell.  It is suspected, though not proven, that viruses are piece of genetic material that have ‘escaped’ from prokaryote and eukaryote cells and have the potential to replicate themselves when they go back into cell environment.

School of Science and Technology, Online Counseling Resource… Types of Viruses  All living things are susceptible to viral infections... plants, animals, or bacteria can all be infected by a virus specific for that type of organism.  Depending upon the type of organism viruses are classified as  Human viruses: These are viruses which infect only humans (for example, smallpox).  Animals viruses: These are viruses which infect only animals (for example, influenza),  Plant virus: viruses which infect only a certain kind of plant (for example, the tobacco mosaic virus).  Bacteriophage: some viruses which infect only a particular species of bacteria (for example, the bacteriophage which infects E. coli).

School of Science and Technology, Online Counseling Resource… Structure  A virus particle, also known as a virion, is essentially a nucleic acid (DNA or RNA) enclosed in a protein shell or coat.  Viruses are extremely small, approximately nanometers in diameter. Adenovirus - Images courtesy of Linda M. Stannard, University of Cape Town. Linda M. Stannard

School of Science and Technology, Online Counseling Resource… Genetic Material  Viruses may have double-stranded DNA, double-stranded RNA, single-stranded DNA or single-stranded RNA.  In different viruses, which of the four is the "genetic material," depends on the nature and function of the specific virus.  The viral genome can consist of a very small number of genes or up to hundreds of genes depending on the type of virus.  Note that the genome is typically organized as a long molecule that is usually straight or circular.

School of Science and Technology, Online Counseling Resource… Protein Coat  The protein coat that envelopes the genetic material is known as a capsid.  It can have several shapes: polyhedral, rod or "complex."  The protein subunits of the capsid are called capsomeres. Papillomavirus - polyhedral capsid

School of Science and Technology, Online Counseling Resource… Specialized Structures  In addition to the protein coat, some viruses have specialized structures.  For example, the flu virus has a membrane-like envelope around its capsid.  The envelope has both host cell and viral components and assists the virus in infecting its host. Capsid additions are also found in bacteriophages  For example, bacteriophages can have a protein "tail" attached to the capsid that is used to infect the host bacteria. Influenza virus Image courtesy of Linda M. Stannard, University of Cape Town.Linda M. Stannard Bacteriophage - Image copyright Dennis Kunkel.Dennis Kunkel

School of Science and Technology, Online Counseling Resource… Bacteriophage:1  Frederick Twort (1915) and Felix d'Herelle (1917) were the first to recognize viruses which infect bacteria, which d'Herelle called bacteriophages (eaters of bacteria).  In the 1930s and subsequent decades, pioneering virologists such as Luria, Delbruck and many others utilized these viruses as model systems to investigate many aspects of virology, including virus structure, genetics, replication, etc.  Some varieties of viruses attack only bacteria. These types are called bacteriophages.

School of Science and Technology, Online Counseling Resource… Bacteriophage:2  The bacteriophage lands on the bacterium and cuts a hole in the cell wall with its 'injection tube'. It then injects its genetic material into the bacterium.  These inserted viral genes take over the bacterium's genetic machinery, and tell the bacterium to begin making new virus parts.

School of Science and Technology, Online Counseling Resource… Bacteriophage:3  These parts come together to make whole new viruses inside the bacterium. Then the bacterium bursts open and dies, releasing all those new viruses to infect more cells.

School of Science and Technology, Online Counseling Resource… Plant Viruses  Plant viruses attack only plants.  They are harmless to all other organisms.  Prevention is the only economic control for virus diseases.  Viruses consist of a nucleic acid core and a protein coat Yellow vein-banding symptoms on grapevine caused by Grapevine fanleaf virus.

School of Science and Technology, Online Counseling Resource… Common Properties of Plant Viruses :1  Plant viruses usually multiply only within living plant cells, but some may be able to multiply within the bodies of aphids and nematodes.  A given plant virus may be able to multiply only within the living cells of one species or genera of plants, but some can multiply within the cells of a wide group of plant families.  In general, most organisms harbor both virluent and and latent viruses.  Temperate viruses embedd them selves within the hosts nucleic acid and are transmitted generation to generation just like genes of the host.

School of Science and Technology, Online Counseling Resource… Common Properties of Plant Viruses:2  Plant viruses usually multiply only within living plant cells, but some may be able to multiply within the bodies of aphids and nematodes.  A given plant virus may be able to multiply only within the living cells of one species or genera of plants, but some can multiply within the cells of a wide group of plant families. Tobacco Mosaic Virus

School of Science and Technology, Online Counseling Resource… Animal Viruses  Animal viruses are intracellular obligate parasites that reproduce only after invading the host animal cell.  There are several types of animal viruses. They are commonly grouped into families according to the type of genetic material present in the virus.  Double-Stranded DNA  Single-Stranded DNA  Double-Stranded RNA  Single-Stranded RNA

School of Science and Technology, Online Counseling Resource… DNA-containing Viruses Herpes viruses are found in a wide range of hosts; at least seven different species are known to infect humans, including herpes simplex. Genital herpes has no cure. Hepatitis B Herpes Virus Adenovirus Papillomavirus Hepatitis B virus causes both acute and chronic liver infections in humans. An unusual feature of these infections are the length of time they last; up to several months in acute infections, and many years (or for life) in chronic infections The papillomavirus attacks human cells, and can cause ordinary warts, which are harmless. But some varieties cause genital warts; these tumours can become malignant The adenovirus consists of a slender shaft with a globular head. Adenoviruses can infect humans, and can cause respiratory illness or conjunctivitis ('pink eye').

School of Science and Technology, Online Counseling Resource… RNA-containing Viruses  Enteroviruses belong to one of the largest families of viruses; others in this family include rhinoviruses (which cause the common cold), cardioviruses, apthoviruses and hepatoviruses (which cause hepatitis A).  Enteroviruses usually reproduce in the intestine. An important enterovirus is the one which causes polio Influenza Enterovirus  The influenza virus causes acute upper respiratory disease in humans, usually accompanied by a fever.  These viruses are roughly spherical, and about 200 millionths of a millimetre in diameter.

School of Science and Technology, Online Counseling Resource… What You Learn…  You have learnt :  Characteristics of viruses  Structure of virus :genetic martial, protein coat  Viruses are on the boundary line of living and non-living.  Types of Plant viruses  Types of animal viruses  Bacteriophages

School of Science and Technology, Online Counseling Resource… Critical Thinking Questions 1.Describe in the detail the structure of viruses. 2.Describe different types of viruses. 3.Write a short not on Bacteriophages 4.What is viruses? Give its different properties. © 2007, YCMOU. All Rights Reserved.30

School of Science and Technology, Online Counseling Resource… Hints For Critical Thinking Question 1.genetic material, protein coat, specialized structures. 2. Animal, plant, Human, bacteriophages, DNA/RNA containg 3.bacteria infecting viruses, structure. 4.Small particles, living/nonliving, self replicating, requires living host for multiplication. © 2007, YCMOU. All Rights Reserved.31

School of Science and Technology, Online Counseling Resource… Study Tips  Book1 Title:The Living World Author: George Johnson  Book2 Title: ABC Of Biology Publisher: Holy Faith  Book3 Title: Biological Science Author: Taylor, Green & Stout

School of Science and Technology, Online Counseling Resource… Study Tips Microsoft Encarta Encyclopedia Wikipedia the free encyclopedia

School of Science and Technology, Online Counseling Resource… End of the Presentation Thank You !