Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Taura syndrome wikipedia , lookup
Elsayed Elsayed Wagih wikipedia , lookup
Human cytomegalovirus wikipedia , lookup
Canine parvovirus wikipedia , lookup
Canine distemper wikipedia , lookup
Marburg virus disease wikipedia , lookup
Hepatitis B wikipedia , lookup
Orthohantavirus wikipedia , lookup
Henipavirus wikipedia , lookup
Chapter 5. Viruses (at the threshold of life) 1. Discovery and Structure of viruses What is virus ? - virus : living things or not ? -> “organules” “molechisms” - Golden age of microbiology (1880 - 1915) -> increased understanding of infectious disease (tuberculosis, typhoid fever..) -> industrial utilization of microbes -> importance of microbes in environments Yet unknown causation of some disease (measles, chickenpox, polio, hepatitis) “ i ” was used “virus” d tto refer f tto unseen or unknown k id identity tit ffor iinfectious f ti di disease - bacterium for tuberculosis - protozoan for malaria caused d b by virus i ? The true nature of virus remained a mystery Chapter 5. Viruses (at the threshold of life) 1) Development of virology - 1892, Dmitri Iwanowski : -> attempting p g to isolate bacterial cause of tobacco mosaic disease -> use filter to trap smallest known bacteria -> filtered juice contained infectious agent -> called filterable virus - 1898,, Martinus Beijerinck j -> diluted filtered juice -> still infectious -> called contagious living fluid - 1930s, Wendell M. Stanley : crystalization of tobacco mosaic virus -> > implies that TMV is chemical molecule -> viral disease caused fever, a response by immune system or other symptom - 1933, electron microscope 발명 -> TMV 전자사진 Chapter 5. Viruses (at the threshold of life) 2) Structure of viruses - size : 27nm(poliovirus) ~ 250nm(smallpox virus) - 500 or more viruses fit inside a single g bacterial cell Chapter 5. Viruses (at the threshold of life) 2) Structure of viruses - shape : helical, icosahedral, complex type HIV Chapter 5. Viruses (at the threshold of life) 3) Component of viruses - genome : core of nucleic acid -> DNA or RNA, not both -> long and helical, or folded -> single molecule, occasionally segmented - caps capsid : coat of p protein -> consisted of capsom capsomeres r s - nucleocapsid : combination of genome and capsid - envelope : membrane-like envelope enclosing nucleocapsid - no cytoplasm ☞ spikes : projections on the envelope -> contacting virus to its host -> assist penetration into host cell Chapter 5. Viruses (at the threshold of life) Chapter 5. Viruses (at the threshold of life) ☞ 생물체로서의 미생물의 특징 - 성장을 위한 영양분의 흡수, 소화 - 소화산물의 배설 - 독립적 생식능력 생물계 구성원의 공통특징 - 환경변화에 대한 적응능력 - 자극에 대한 반응능력 ☞ virus의 생화학적 특징 - no chemistry going on within a virus - no intake of nutrient - no production of waste - no increase or decrease in size - no metabolism - but, they replicate -> p programs g a host cell biochemicallyy to p produce hundreds of copies p Chapter 5. Viruses (at the threshold of life) 2 Viral replication 2. - virus : inert particle outside a host cell -> becomes highly efficient replicating machine in the host cell -> utilize metabolism of the cell -> produces multiple copies of itself in several stages 1) Stages of replication (1) attachment stage - high degree of specificity for a certain host - 1. protein molecule in envelope keys off receptor sites(lock) in the host cell - 2. or viral tail attaches to receptor sites - 3. or blending of viral envelope with host cell membrane - 4. or by phagocytosis X 200,000 Viral attachmnet X 70,000 Chapter 5. Viruses (at the threshold of life) (2) penetration stage - nonenveloped virus is left outside the host cell, the genome passes into the cell (3) uncoating stage - within the cell, cellular protein removes the protein capsid from the viral genome (4) synthesis stage - viral proteins are synthesized from viral genome using cellular machinery (5) assembly stage - viral parts are combined to form new viral particles after synthesis is completed (6) release stage - viral envelope is built from cellular membrane -> disrupt cell membrane => lytic cycle Replication p of Enveloped p virus Clickk to view Cli i animation. animation Unenveloped virus Chapter 5. Viruses (at the threshold of life) 2) L Lytic tic and llysogenic s enic c cycle cle - some times, virus enters a host cell but do not replicate immediately =>lysogeny - lysogenic y g cycle y : -> virus incorporates its genes into the host genes and becomes part of it -> multiply together with host genes => becomes provirus(oncogene) Chapter 5. Viruses (at the threshold of life) Lytic and lysogenic cycle Chapter 5. Viruses (at the threshold of life) Lysogenic and lytic cycle Clickk to view Cli i animation. Clickk to view Cli i animation. animation Chapter 5. Viruses (at the threshold of life) 3) Viriods and prions - Viriods : single-stranded molecules of RNA without protein coat -> infect plants causing disease - Prions : proteineous infectious particle -> composed solely of protein, extremely stable -> transformed from prion protein(PrP, harmless protein in itself in brain cell) -> PrP : protect cells by helping rid of dangerous chemicals -> prion : clump together -> block molecular traffic 3 Viruses and Cancer 3. - Cancer : results from uncontrolled reproduction of cells -> grows into abnormal, functionless mass of cells => tumor - body’s response to the tumor -> surrounding it with a capsule of connective tissue => benign -> outgrowth and break out of the capsule and spread => malignant - Properties of cancer cell differing from normal cells -> more rapid growth than normal cell -> stick together less firmly than... -> undergo dedifferentiation (reverting to an early stage to divide indefinitely -> fail to exhibit contact inhibition -> not stop growing when contacted Chapter 5. Viruses (at the threshold of life) Contact inhibition Chapter 5. Viruses (at the threshold of life) ☞ How viruses transform cells - oncogene : transforming genes normally reside in the chromosomal DNA of cells -> not viral in origin but part of the genetic endowment -> > over 60 oncogenes were identified - proto-oncogene : fore-runners of oncogenes -> can be converted to oncogenes by carcinogens including viruses