October 31 notes

Microbiology, Halloween 2008: A scary story about smallpox
Review of DNA replication:
*oriC site (start of DNA replication) {DnaAhelicase}”replication bubble”
*SSB protein covers strands of DNA
*DNA polymerase: 5’3’ brings in new matching bases, synthesizes new sugar-phosphate backbone
*Okazaki fragments patched together
*last step: new DNA strand has methyl groups added to A& Ts
E. coli replicates DNA at a rate of 1,000 new bases/second!
Mutation: change in DNA sequence
*effect of mutation usually neutral but can be bad or goodE. coli R to T4
Genome sizes:
*Mycoplasma genitalum ~ 600,000 bps in chromosomes
*T. pallidum (cause syphilis & must live in host cell) ~ 1 million bps
*S.aureus (almost always live on people’s skin) ~ 3 million bps
*E. coli (can live in lots of places) ~ 5 million bps
*B. anthracis (lives in soil, sometimes in people, but not for a long time) ~ 6 million bps
*Viruses have smaller genomes than M. genitalum
*Mitochondria also have very small genomes (~size of viral genome)
*More reliant on other organisms, more reduction in genome
Ex.: viruses use host enzymes to copy viral DNA, so don’t need to have own genes for
replication enzymes
II. Human protection against viruses
a. Immune defenses:
*acquired immunity:
Exposed to virusmake antibodies
if re-exposed, won’t get sick
*very few antiviral drugs

b. Vaccination: Get an acquired immune response, but don’t get illness
c. Disease Education:
*If disease caused by microbe that relies on host to reproduce, if you can keep microbe from
spreading for one cycle, you can wipe out forever

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