Basic Structure and Components and History Flashcards
Basic Structure and Components
-Virus are small infectious agents and consist of nucleic acid genome (either DNA or RNA)
-genetic material enclosed by protein coat called capsid.
-Additional layer of proteins and lipids are in some viruses which is derived from host cell’s membrane
-BASIC VIRAL STRUCTURE IS 3 COMPONENTS=the nucleic acid genome, capsid and in some cases, an envelope
Nucleic Acid Genomes
-This is the genetic material of virus
-Can be DNA or RNA
-Genome has all instructions for virus to replicate in the host cell
-some viruses can also carry enzymes that aid in replication such has reverse transcriptase(used by retroviruses to convert RNA to DNA)
Capsid
-This is the protein shell that encloses the genome
-Made of protein subunits called capsomeres
-they can self assemble into a 3D structure
-The capsid protects viral genome and plays role in attaching to host cells during infection
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Envelope
-not all virus have this
-this envelope is derived from the host cells membrane and contains proteins that aid in attachment and entry to host cell
-Also helps protect the virus from host immune responses and environmental factors
History
-3700 BC first written record of virus infection in Egypt which shows priest showing clinical signs of paralytic poliomyelitis
-1193 BC, the mummy shows left leg withered away and food extended like horse hoof which is sign of paralytic poliomyelitis
-1143 Ramesses V mummy shows he died of smallpox at 35 age. Pustular lesions of face are similar to recent subjects.
-1000 BC smallpox is endemic in CHINA (variolation=immunizing patients against smallpox by infecting them with mild form).
-1520 smallpox from Europe went to americas and 3.5 million Aztecs died in 2 years which ended the Aztec empire
-1796 edward jenner vaccinated 8 year old with cowpox lesion on hand of a milk maid who never had small pox and healed in 2 weeks. He was then challenged with real smallpox
-1892 Dmitri Iwanowski who is a russian botanist showed extracts from tobacco plant can transmit disease to other plants after passage through ceramic filters which were fine enough to retain the smallest known bactera (START OF VIROLOGY)
-1892 Martinus Beijerick found a agent that could reproduce only in host and was not inactivated by alcohol. agent was described as contagious living liquid. Stated is was not bacteria or fungus or other culturable pathogen. Father of Virology
Important People
-Felix Dherelle followed fredrick tworks work and recognized viruses which infect bacteria and called them bacteriophages (eaters of bacteria)
-Wendell Stanley crystallizes tobacco mosaic virus and shows it remains infectious, got the nobel prize and his work helped describe the molecular structure of any virus. Named after stanley hall
-Max theiler was the first to propagate yellow fever virus in chick embryos and produce a attenuated vaccine 17D strain and it was so good and safe that we still use it. Saved millions of lives and models future vaccines and was given nobel prize in 1951
-1945 had salvador luria and alfred hershey who showed that bacteriophages mutate. Nobel prize 1969. Work proved that similar genetic mechanisms operate in viruses as in cellular organisms and laid basis for understanding of antigenic variation in viruses
-1950 the world health organization proposed a program to stop smallpox in america and was acheived in 8 years
-alfred hershey and marth chase showed that DNA was genetic material of bacteriophage.
-Polio vaccine discovered by Jonas salk and it was licensed in 1955 and was 70% effective
-1957 Heinz Conrat and RC williams showed that mixtures of purified tobacco mosaic virus RNA and coat protein were incubated together and the virus particles formed spontaneously. Indicates that particle was in free energy minimum state and was favoured structure of the components.
-Baruch Blumberg found the HBV got nobel prize in 1976 and developed the first vaccine against cancer since HBV strongly associated with liver cancer
-Howard Temin and David Maltimore find reverse trancription in retroviruses (nobel prize 1975)discovery of reverse trancription led path for genetic info to flow from RNA to DNA and refuted the so call central dogma of molecular biology
-1979 smallpox eradication was a big success and the last known natural cause was in somalia in 1977, smallpox is one of 2 infectious diseases to be eradicated and the other is rinderpest of 2011
-Since then only known cases of small mox were lab accidents with killed 1, nothing in the past 25 years and there is a major worry for bioterrorism since the british used smallpox as biological warefare in the 1700s
-1983 had Luc Montaigner and Robert Gallo discovered HIV being the cause of AIDS and in 2 years after the start of AIDS, the agent was discovered
-2009 we see swine flu mexico had 900 cases and level 3-4 pandemic and spread slow
-2016 had Zika and Ebola viruses in south america and central america/ Level 2 threat. Zika virus transmission and women becoming pregnant was a big scare, 3500 micro cases and infants had severe microcephaly and some died
-2020 was covid
-now, we hope polio will soon be the second viral disease to be wiped out, Hepatitus B has an effective world wide strategy but liver cancer caused by viral infection will continue, Measles has a good vaccine since 1963 and can be eliminated, and influenza has an effective strain specific vaccine made every year but there are new dangerous strains that mutate
- HIV has no vaccine and drugs are effective by are costly and toxic, and drug resistance appear fast, 50 mill infected, ebola is also the most dangerous with a mortality rate of 70-80% but vaccine is being made
-Covid19 as of march 2022 there has been 6 million deaths
Fact
Share our bodies with numerous viruses that cause hepatitus, respiratory desease, mononucleosis, diarrhea, gental warts, herpes, and forms of cancer
