Chapter 13 - BSC 1010 Dr. Presley Chapter 13 GENETICS OF...

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BSC 1010 Dr. Presley Chapter 13 Advantages for study of genetics using microbes: Smaller amount of DNA is easier to work with Bacteria have 1/1000 the DNA of human Virus have 1/100 the DNA of a bacterium. Easy to produce large numbers of the organisms in the laboratory Escherichia coli divides every 20 minutes and viruses even faster. Also useful as tools in biotechnology and environmental recycling Both important pathogens affecting humans or their food sources VIRUS -original name: contagium vivum fluidum , shortened to virus which means “poison” -acellular ? living – cannot be cultured on media, cannot be killed by alcohol ? -very small (non-filterable) –note size in Table 13.2 on page 258 millions can fit on a pinhead -obligate intracellular parasites -genome = nucleic acid core (DNA or RNA, linear or circular, single or double-stranded) Study Table 18.1 on page 334 **Virion – virus outside of host cell -protein coat ( capsid made up of protein subunits called capsomeres) Shapes: helical, polyhedral, enveloped, complex ---- Study Fig 13.1 on page 259 -envelope (host cell membrane + glycoprotein spikes) -unable to reproduce outside of living host cell -unable to metabolize energy -unaffected by antibiotic treatment (since antibiotic action is on metabolic process) **Prophage – dormant viral DNA integrated in host chromosome in lysogenic cycle **Bacteriophage – viruses which infect bacteria Related classifications: Viroid – circular, single-stranded RNA only (no coat), found only in plants prions - infectious proteins – mad cow disease (page 343 in Ch 17) VIRUSES CLASSIFIED ACCORDING TO : 1. Type of nucleic acid a. double-stranded DNA Papovavirus – causes cervical cancer, warts Herpesvirus – Herpes simplex I-cold sores; II – genital sores; Varicella zoster – chicken pox, shingles; Epstein-Barr virus – mononucleosis Poxvirus - smallpox b. single-stranded DNA Parvovirus - roseola c. double-stranded RNA Reovirus – diarrhea, mild respiratory disease d. single-stranded RNA that serves as mRNA Picornavirus – poliovirus; rhinovirus (common cold); enteric viruses Togavirus – rubella virus; yellow fever virus; encephalitis virus e. single-stranded RNA that serves as template for mRNA Rhabdovirus – rabies Paromyxovirus- measles; mumps Orthomyxovirus – influenza viruses f. single-stranded RNA that serves as template for DNA synthesis Retrovirus – RNA tumor viruses (leukemia viruses); HIV (AIDS virus) 2. Shape Study Fig 13.1 on page 259 a. Helical ex. tobacco mosaic virus b. Polyhedral adenovirus (respiratory infections) c. Complex d. Enveloped (membranous envelope with glycoprotein spikes) influenza virus (p. 262) 3. Host range / tissue specificity ex. bacteria (bacteriophage), plant virus or animal virus “New virus” is not really new but just expanding its host territory VIRAL REPRODUCTION
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Chapter 13 - BSC 1010 Dr. Presley Chapter 13 GENETICS OF...

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