Powerpoint 28 Flashcards
starts at a specific sequence called the Origin of replication
Replication
One original parent strand and one newly synthesized daughter strand rewind
Replication
referred to as Semi-conservative*
DNA replication
makes DNA
DNA polymerase
is bi-directional
DNA replication
provide organism way to respond to changing environments
- changes morphology and affects the buoyancy
Mutation
Environment selects* for cells suited to survuve
- environment doesnt CAUSE it.
- CAUSE is replication error or failed to repair
utation
most similar to the original isolate
wild-type strain
a mutant that requires specific growth factor
Auxotroph
An organism that does not require addition of growth factor
Prototroph
The information related to the gene sequence
Genotype
The output or consequence of gene mutation
phenotype
Base substitution
- most common type of mutation
- results from mistakes during DNA syntheses
- incorrect bae is incorporated into DNA
Spontaneous mutations
occur when one base pair is changes
point mutation
mutation resulting from amino acid substitution is called
missense mutation
mutation that changes a amino acid codon to a stop codon
Nonsense mutation
How many codons make up the alphabet of proteins
64
Of the 64, how many code for specific amino acid?
61
the remaining 3 code for
termination of the protein
code for sereine
UCG
stop codon
UAA
repair of base substitution can be done by
- proofreading
- mismatch repair
- 1 component
- DNA polymerase has proofreading function
- Able ro excise incorrect base and replace with corret on
Proofreading
- multiple components
- endonuclease enzyme removes short stretch of nucleotide
- DNA polymerase fills gap
- DNA ligase joins ends
Mismatch repair
Two mechanisms help the repair of thymine dimers
- light repair
- dark repair
a. k.a. photoreactivation
- enzyme uses visable light to break covalent bonds between basses
light repair
aka exision repair
- endonuclease excises damages section
- new section replicated and joined to original strand
dark repair
- last dich effort to bypass damage
- damage induces SOS system
SOS repair
produces new DNA polymerase
- Highly error prone
- mutations can arise from synthesis with new enzyme
SOS repair
major problem with induced mutation is
identifying bacteria with desired mutation
involved inoculating population of bacteria on medium on which only mutants will grow
direct selection
used to select antimicrobial resistant organisms
direct selection
required to isolate organisms that require growth factor that parent strain does not
indirect selection
replica plating
indirect selection
testing for cancer causing chemicals
-many mutagens are also carcinogens –> cancer causing agents
AMES test
Microbes used to test potential carciogenitc activity
AMES
The AMES tests are based on effect chemical had on
microbal DNA
Test the rate of reversion of Salmonella auxotroph
-also tests potential lethality
Ames common chemical carcinogen test
