Transcript Slide 1 - Fort Bend ISD

CHAPTER 18
Microbial
Models: The
Genetics of
Viruses and
Bacteria
Size
Averages
Eukaryotic
10 um.
Bacteria 1 um.
Viruses .1um.
Respiratory
infections & pink eye
The human Papilloma virus causes warts and cervical cancer
double stranded circular DNA
Adenovirus causes
respiratory infections and
pink eye
Bacteriophages
Simplified viral
reproductive cycle
double stranded DNA
Lytic cycle of a T4 phage
Parts selfassemble
The lysogenic and lytic reproductive
cycles of phage lambda a temperate phage
The reproductive cycle of
an enveloped virus with a
single stranded RNA
genome but not a
retrovirus
Structure and
Life Cycle of an
HIV virus
a retrovirus
HIV infection
Ebola virus-too virulent?
Deer mouse
Hanta virus
Vaccines- ”harmless” variations of the virus that initiate the
immune system to form memory T-cells and B-cells
Synthetic vaccines-made from other viruses usually the smallpox
virus with recombinant DNA technology, no possible infection
Tobacco mosaic virus
Tobacco mosaic virus
Viroids
Tiny molecules of naked circular RNA. They do not
encode proteins but they can replicate in host cells
using the hosts cells enzymes. They seem to only
affect plants. Some how they disrupt metabolism of
the plants and cause errors in regulation of protein
synthesis. Affects tomatoes, potatoes, and palm
trees
Prions
Infectious protein molecules that can somehow replicate
in cells. They cause degenerative brain diseases. They
cause scrapie in sheep, “mad cow disease” or bovine
spongiform encephalitis, and Creutzfeldt Jacob disease
in humans. Cause the normal form of a protein to fold
up wrong and thus become a prion.
RESTRICTION ENZYMES
RESTRICTION ENDONUCLEASES
Produced by bacteria for protection from viruses, they
cut DNA at specific recognition sites and prevent it
from taking over the cell. They can all be called
endonucleases. They often make uneven cuts that
leave short single-stranded pieces on each end called
“sticky ends”
How do bacteria keep their own DNA from being cut
by their restriction enzymes?
Methylate their restriction sites
How are restriction enzymes used in recombinant DNA
technology?
Normal without an F+
episome
Replication of the
bacterial chromosome
begins at one origin
and continues in both
directions
Detecting genetic recombination in bacteria
So, what happened?
Conjugation and recombination in E. coli
Plasmids-small rings of DNA that contain 2 - 30 genes
and can replicate on their own when in a cell by rolling
circle replication
R plasmids contain genes for antibiotic resistance
How could several genes for antibiotic resistance end
up on the same plasmid?
Transposons
Conjugation and recombination in E. coli
Conjugation and recombination in E. coli
F-pili
Insertion of a
transposon
and creation of
direct repeats
Anatomy of a composite transposon
The trp operon a Repressible Operon
Tryptophan absent, repressor inactive, operon on
The trp operon a Repressible Operon
Tryptophan present, repressor active
The trp operon a Repressible Operon
Tryptophan present, repressor active, operon off
The lac opreron: an inducible operon for enzymes
that are only needed occasionally
What would happen if a mutation to the regulator gene
produced a defective repressor protein?
What would happen to the levels of the mRNA and the
enzymes after all available lactose was digested?
Smallpox
Measles
Measles
Polio
Hepatitus
Killed 300,000 worldwide
Began in 1918
Herpes
E. coli DNA
plasmids