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VARIETY OF LIFE
- 1. VARIETY OF LIFE Chapter # 05
- 2. VIRUS virus = Poison Iwanosky in 1892 Minute Non-cellular between living & non-living entity
- 3. 1. non-cellular 2. obligate parasites. 3. cannot live & reproduce outside the living body. 4. size range ----20nm-250nm. 5. virulent / temperate. CHARACTERISTICS OF VIRUS
- 4. STRUCTURE OF VIRUS Spherical rod-shaped Tadpole polyhedral
- 5. STRUCTURE OF A COMPLICATED VIRUS 1. viral genome 2. capsids 3. envelopes 4. Tail 5. tail Fibers
- 6. CLASSIFICATION OF VIRUSES ON THE BASIS OF MORPHOLOGY Rod shape (TMV) Spherical (Polio Virus) Tadpole (Bacteriophage Virus)
- 7. ON THE BASIS OF MODES OF ORIGIN 1. Naked +strand viruses. 2. Enveloped +strand RNA Viruses. 3. Minus strand RNA Viruses. 4. Viroids CLASSIFICATION OF VIRUSES
- 8. ON THE BASIS OF MODES OF ORIGIN 5. Double strand RNA Viruses. 6. Small genome DNA Viruses. 7. Medium genome and large genome DNA Viruses. 8. Bacteriophage. CLASSIFICATION OF VIRUSES
Editor's Notes
- Viruses are very SMALL non cellular bodies considered between living and non-living ORGANISMS. وائرس اور ان کی وجہ سے ہونے والے انفیکشن کا سائنسی مطالعہ انیسویں صدی کے اختتامی برسوں میں شروع ہوا۔ تھے کہ وائرس موجود ہیں۔ وائرس کے وجود کا پہلا ثبوت ان فلٹرز کے تجربات سے سامنے آیا اگرچہ لوئس پاسچر اور ایڈورڈ جینر نے وائرل انفیکشن سے بچنے کے لئے پہلی ویکسین تیار کیں ، لیکن وہ نہیں جانتے The term virus is derived from a Latin word meaning “Poison”. A Russian Biologist Iwanosky in 1892 discovered Virus.
- An obligate parasite is a parasitic that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. ایک نینو میٹر ایک ملی میٹر کا دس لاکھواں حصہ ہے Viruses that are capable of using both modes of reproduction either lytic or lysogenic with in a bacterium
- Poliovirus spreads from person to person and can infect a person's spinal cord, causing paralysis TMV was the first virus Tobamovirus infects a wide range of plants, especially tobacco and other members of the family Solanaceae. Polyhedral viruses consist of nucleic acid surrounded by a polyhedral (many-sided) shell or capsid
- Viral genome may be composed of a single or many molecules of DNA or RNA. The protein cover present around the genome is called capsid. Each sub-unit of capsid is called “capsomeres” In some viruses some extra envelopes are present that help them in infecting their host. They are membranous structures present around the capsid. Some viruses possess proteinaceous tail and tail fiber. The tail and tail fiber help in infecting the host.
- PLUS STRANDED genome can act as messenger RNA (mRNA) and can be directly translated into viral proteins by the ribosomes OF host cell. MINUS STR AND GENOME act as complementary strands from which messenger RNA (mRNA) is synthesized Viroids are the smallest known infectious pathogens. They are composed ONLY of a short strand of circular, single-stranded RNA that has no protein coating. All known viroids are inhabitants of higher plants,
- RNA viruses generally have very high mutation rates compared to DNA viruses, because viral RNA polymerases lack the proofreading ability of DNA polymerases. This is one reason why it is difficult to make effective vaccines to prevent diseases caused by RNA viruses A mutation is a change in a DNA sequence