PPT-Viral origin What are viruses?

Viruses are acellular organisms completely obligatory parasites The term virus means poison Most of them are disease causing Have a complex mechanism of hijacking the machinery of the host genome for its self replication. Chapters 12 and 13. Viral Characteristics and Structure. Why Viruses aren’t Alive. General Characteristics of Viruses. Name derives from the Latin for “poison”. Obligatory intracellular parasites. A. Viruses are a unique group of biological entities. 1. They are not capable of surviving without a host cell (lack metabolic machinery). 2. They do, however, contain all the information necessary to direct metabolic processes. What is a Virus?. Very small . Non-living particle. Made up of nucleic acid. . and proteins. Can only reproduce by infecting living cells. Do not carry out respiration, grow or develop. Structure. Viruses have an inner core which contains either RNA or DNA. Infectious Agents of Animals . and Plants. Chapter 14. What am I?. Structure and Classification of Animal Viruses. Classification of animal viruses. Taxonomic criteria based on. Genomic structure. DNA or RNA. Viruses Are Not Cells!. There are several structural and functional differences between cells and viruses. The structural differences include:. No nucleus. No cell membrane. No organelles. The functional differences include:. Chapter 18. Are Viruses Alive?. As a group discuss for 1 minute. Be able to defend your answer for the class!. Are . VIRUSES. alive?. Growth and Development. Reproduce. Change Over Time. Obtain and Use Energy. EQ: Why are viruses considered to be non-
living?. Characteristics:. *Nonliving particles made of . nucleic acid. and a . protein coat . enlosed in a . capsid. shell... *In order to reproduce, all viruses must have a . VOCABULARY. Virus. Capsid. Envelope. Human . Immunodeficiency Virus (HIV. ). Influenza. Lytic Cycle. Lysogenic Cycle. Lysis. Retrovirus. Prerequisite questions. What are the eight characteristics which all living things have in common. Claude MUVUNYI M.D., Ph.D.. Viral diseases. The relative susceptibility of a person and the severity of the disease depend on factors such as: . the . nature of exposure; . the . immune status, . age. use many of the host cell’s biochemical mechanisms and products to sustain their viability. A mature virus(virion) can exist outside a host cell and still retain its infective properties.. . 3. the virus. arboviruses. ) are viruses that can be transmitted to man by arthropod vectors. . Arboviruses. belong to three families:. Togaviruses. . Bunyaviruses. e.g. . Sandfly. Fever. .. Flaviviruses. e.g. Yellow Fever, dengue, Japanese Encephalitis. . . The process of transfer of virus into host is referred as . TRANSMISSION. and this is an important step in the life cycle of viruses.. Person to person infections are said to be . HORIZONTAL. . As a group discuss for 1 minute. Be able to defend your answer for the class!. Are . VIRUSES. alive?. Growth and Development. Reproduce. Change Over Time. Obtain and Use Energy. Maintain Homeostasis. Viruses are very small – smaller than the smallest cell.. They are usually surrounded by a capsid of proteins.. For replication, viruses rely on their host cells . ie. ., the cells they infect.. Most viruses exhibit a limited host range- they typically infect only specific types of cells of one host species..