Genetics of Viruses and Bacteria. Bacterium. Virus. Animal cell. 0.25 µm. Animal cell nucleus. Virus Size. Bacteria are prokaryotes w ith cells much smaller and more simply organized than those of eukaryotes Viruses a re smaller and simpler than bacteria.
Virulent Viruses-reproduce only by lytic cycle
It uses host materials and machinery to produce capsid proteins
Viral DNA and capsid proteins assemble into new virus particles, which leave the cell
The SARS-causing agent is a
coronavirus like this one
(colorized TEM), so named for
the “corona” of glyco-protein
spikes protruding form the
Young ballet students in Hong
Kong wear face masks to
protect themselves from the
virus causing SARS.
Green tomato infected with tomato spotted wilt virus
INFECTIOUS PRION PROTEINS have a different shape, which they impose on normal prion proteins in a chain reaction that ends in sickness and death.
A hypothesis of how infectious protein particles, or prions, cause disease: PrPSc - an abnormal protein - communicates with its normal twin - PrPc - creating an abnormal form, that will eventually harm neurons.
(Adapted by Leigh Coriale Design and Illustration, with permission, Science [July 12], 1996, American Association for the Advancement of Science.)
Kuru Infected Brain
It exists only among a single tribe in Papua New Guinea. The afflicted tribe - the Fore Highlanders - describe it as the "laughing death", because it leads to loss of coordination accompanied by dementia.
Gene transfer occurs separately from bacterial reproduction
Transposase geneInsertion Sequences
Genes of operon
Polypeptides that make up
enzymes for tryptophan synthesis
Tryptophan absent, repressor inactive, operon onLE 18-21a
Both plates of E.coli are transformed by pGLO plasmid as seen by growth on LB with ampicillin. The upper plate also contains arabinose, the inducer for the green fluorescent protein. This is visualized under UV light. The lower plate does not glow even though it has transformed cells because the media lacks arabinose.