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VIRUSESReading AssignmentWhy viruses don’t have scientific namesPlasmidsViruses are smaller than cellsViral diseasesStructure of VirusesReverse transcriptaseEntry of viruses into cellsWays of slowing disease spreadVaccination & Immune systemVaccinationVaccinationPopulation dynamicsThe Lytic Cycle of bacteriophageLysogenic replication is alternative to lytic cycleEmerging viruses -emerging diseasesNew Viral DiseasesOrigin of a new diseaseVocabularyLecture 12 Exam 1 UIC BioS 101 Nyberg 1VIRUSESViruses can replicate only in a living cell. They require molecules made by their hosts for transcription and translation. Virus are, therefore, not considered to be organisms.Lecture 12 Exam 1 UIC BioS 101 Nyberg 2Reading Assignmentz Chapter 35.z Read Bioskills 10, Biological Imaging.z Monday, 14 Feb 11, is the first BioS 101 exam.z You will sit in sections according to your teaching assistant. z Complete the scantron answer sheet information at the beginning of the exam. DO NOT WAIT until the end of the exam.Lecture 12 Exam 1 UIC BioS 101 Nyberg 3Why viruses don’t have scientific namesz Viruses can multiply only within the cells of host organisms.z Viruses don’t code for their own ribosomal RNA (which is what ‘tree of life’ is based on).z Viruses definitely evolve and exploit variation to avoid host defenses.Lecture 12 Exam 1 UIC BioS 101 Nyberg 4Plasmidsz Plasmids, usually circular DNA, can infect certain cells.z Plasmids never form a capsid (protective cover). –that distinguishes them from viruses.z The R plasmid carries resistance to many antibiotics and spreads from benign bacteria to species that cause disease.Lecture 12 Exam 1 UIC BioS 101 Nyberg 5Viruses are smaller than cellsz Because they are small, the abundance of viruses is very high (see picture on p 675).z Small particles essentially float in air.z Viruses get from person to person by air and direct contact. I know of no human viruses primarily transmitted by water.Lecture 12 Exam 1 UIC BioS 101 Nyberg 6Viral diseasesz When a disease effects a large number of individuals at the same time it is referred to as an epidemic.z A virus or organisms that is able to kill the host after infection is called virulent.z A big epidemic was the ‘Spanish Flu” of 1918-1919.Lecture 12 Exam 1 UIC BioS 101 Nyberg 7Structure of Virusesz All viruses store hereditary information in nucleic acids, but only a small proportion of viruses use double-stranded DNA.z All viruses have a protein coat called a capsid.z Enveloped viruses are surrounded by a lipid layer derived from the host. The others are said to be nonenveloped.Lecture 12 Exam 1 UIC BioS 101 Nyberg 8Reverse transcriptasez Some viruses use RNA to store information.z Many of these viruses, HIV included, make DNA complementary to the RNA. This is done with an enzyme call ‘reverse transcriptase’ (because it copies info from RNA to DNA the reverse of transcription.)z Reverse transcriptase has been a very important enzyme for research.Lecture 12 Exam 1 UIC BioS 101 Nyberg 9Entry of viruses into cellsz Breathing, wounds and bites are ways viruses can initially get inside an individual, but this does not tell us how the virus spreads among cells of the body.z Cells have proteins on their surface (doing many tasks). Most viruses attach to particular proteins and enter the cell thru that attachment.Lecture 12 Exam 1 UIC BioS 101 Nyberg 10Ways of slowing disease spreadz Public health involves protecting the population from disease.z Quarantine is an effective means of stopping the spread of many viral diseases.z For diseases that spread by intimate contact developing a list of contacts is information that can be used to combat the spread.Lecture 12 Exam 1 UIC BioS 101 Nyberg 11Vaccination & Immune systemz The immune system defends the body against ‘exotic’ molecules.z One’s own molecules were inventoried early in life.z The immune system primarily recognizes proteins as they have many shapes.z Continued detection of the exotic molecule results in a stimulation of the cells that recognize it to grow and become more abundant.Lecture 12 Exam 1 UIC BioS 101 Nyberg 12Vaccinationz Viral proteins, killed viruses or attenuated viral particles are injected into an individual.z The injected material stimulates the immune system to produce antibodies. The molecule the antibodies recognize is called an antigen.Lecture 12 Exam 1 UIC BioS 101 Nyberg 13Vaccinationz Vaccination prepares the immune system to respond to a disease that it has not yet encountered. z People who have been vaccinated will respond by quickly producing antibodies if the virus infects them later.z Vaccinated individuals are said to be immuneto a particular disease.Lecture 12 Exam 1 UIC BioS 101 Nyberg 14Population dynamicsz Contagious diseases typically can spread from individual to individual only a a particular stage or time period.z If many individuals are immune to a disease the rate of spread is reduced. At some point the disease dies out because it can find no never-infected individuals.Lecture 12 Exam 1 UIC BioS 101 Nyberg 15The Lytic Cycle of bacteriophagez Nucleic acid injectionz Nucleic acid replicationz Translation into proteinz Capsid proteins surround nucleic acid.z Host cell bursts open and the viral particles are released.Lecture 12 Exam 1 UIC BioS 101 Nyberg 16Lysogenic replication is alternative to lytic cyclez Sometimes viral DNA integrates into the host DNA instead of replicating and making more viruses.z In that state it causes no problems to host and does not produce viral proteins -until something causes it to ‘pop out’ of host DNA.Lecture 12 Exam 1 UIC BioS 101 Nyberg 17Emerging viruses -emerging diseasesz Diseases are NOT permanent components of the human ‘landscape’.z Most of the viral diseases that we are concerned with today did not exist as human diseases a few hundred years ago.z A pathogen that jumps from animal into human populations is called a zoőnosis.Lecture 12 Exam 1 UIC BioS 101 Nyberg 18New Viral Diseasesz Hanta virusz Ebola virusz West Nile virusz HIVz SARSz Severe acute respiratory syndromez Severe = serious, really sickz Acute = rapid progression from onset to really sickLecture 12 Exam 1 UIC BioS 101 Nyberg 19Origin of a new diseasez How does one figure out the probable source of a new viral disease?z Identify the earliest cases.z Look for common elements shared among the earliest cases.z Use knowledge/experience of other epidemics to focus on likely common


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UIC BIOS 101 - VIRUSES

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