Genetics of bacteria Flashcards
Define a wild type strain
A strain isolated from nature
Briefly describe the difference between selectable and non-selectable
mutations and give an example of each. Which one requires screening for
detection?
Selectable mutations give the mutant a growth advantage under certain conditions, they’re useful in genetic research an example is drug resistance
Nonselectable mutations don’t give an advantage nor a disadvantage over the parent, they need large colonies to see a difference. They need screening
Describe how replica plating works and what category of mutation can it be used to
detect.
1) The masterplate is pressed on to velveteen
2) The velveteen now has an imprint of all the colonies
3) Imprints of colonies are transferred to fresh media (complete and minimal)
It is used to screen for non selectable mutants
Describe the difference between spontaneous ,induced mutations and point mutations
Spontaneous occurs without external intervention
Induced are made on purpose or environmentally (can come from radiation)
Point mutations are mutations that only change one base pair
What is the difference between
Silent mutation:
Missense mutation:
Nonsense mutation:
Silent mutation: no affect to a. acid sequence
Missense mutation: A. acid changed, polypeptide altered
Nonsense mutation: codon becomes a stop codon, polypeptide is incomplete
Briefly describe a bacterial test that can be used to test potentially hazardous
chemicals.
Ames test
Looks for an increase in mutation in presence of mutagen. A wide range of chemicals have been screened for toxicity
Done by filter discs soaked in chemicals to see if mutagenic
Define each of the following.
(i) Recombination.
(ii) Homologous recombination.
Recombination: Physical exchange of DNA between genetic elements
Homologous recombination: Process that results in genetic exchange between DNA from two different sources
What is transformation
Genetic transfer where DNA is put into a recipient cell and brings about genetic change
Discuss what is meant by the term “plasmid”. Detail applications associated with plasmids.
Plasmids are circular pieces of DNA that carry their own genes for specialised function. Some carry the ampR gene which has ampicillin resistance.
They are a way to introduce foreign genes into bacterial cells
What is transduction and what are the two types?
Transduction is the transfer of DNA from one cell to another vis bacteriophage
Generalised: DNA from any part of the host is put inside the virion. Low efficiency, defective virus joins cells chromosome randomly
Specialised: DNA from a specific part of the host is put inside the virion. Transducing efficiency can be high
Discuss conjugation as a mechanism of genetic transfer
Method of genetic transfer that needs Cell to Cell contact, it also needs plasmids to work. It contains Doner cell which has a plasmid and a recipient cell that does not. It has a sex pilus and DNA is synthesised by rolling circle application which is needed for DNA transfer
Why does genetic manipulation of archaea lag behind?
Archaea need to be grown in extreme conditions
Most antibiotics dont work on them
There is no single model organism for archea
