micriobial genetics Flashcards
replicon plasmid meaning
plasmids can autonmously replicate
episome plasmid meaning
plasmids that can integrate in the host chromosome
transposons def
mobile DNA sequences that can move between plasmids and the chromosome
what is the repository for many antibiotic resistance genes
transposons
degradative plasmids
contains genes that code for enzymes involved in catabolism of complex compounds
Col plasmids
contain genes that code for bacteriocins, proteins that can kill other bacteria
pathogenicity islands (PAIs)
sections of DNA that encode virulence factors w originated from another organism
what is a bacteriophage
virus that replicates inside a bacteria
consists of nucleic acid encapsulated in a protein coat
infection of bacteria by virulent phage will result in what
result in death by cell lysis (releases newly replicated phage particles)
prophage
in the lysogenic state the phage genome integrates in the bacterial chromosome and will be replicated w the bacterial genome
conjugation gene transfer
cell-cell contact
form cytoplasmic bridge
requires sex pilus hair like projection
conjugation gene transfer
cell-cell contact
form cytoplasmic bridge
requires sex pilus hair like projection
must have 1 F+ cell and the F- recipient will then become F+
Hfr vs F+
F+ strains and Hfr is that F+ strains have F plasmids in the cytoplasm freely without integrating into bacterial chromosomes while Hfr strains have F plasmids integrated to their chromosomes.
transduction gene transfer
via phage vector w/o cell-cell contact
phage will infect recipient
can be generalized transduction or specialized transduction
generalized transduction vs specialized transduction
generalized - phage DNA to be completely replaced by the bacterial DNA
specialized transduction - DNA consists of both phage DNA and bacterial DNA
transformation gene transfer
transfer of genes by means of naked DNA
the recipient must be competent (have structures on its cell wall that can bind the DNA and take it intracellularly)
Griffith experiment results and methods
isolated streptococcus pneumonia
lead to discovery of DNA as genetic material
capsules produced “smooth” (S) mucoid colonies (lethal)
mutants w/o capsules grow as “rough” (R) colonies (non lethal)
spontaneous mutations
due to uncorrected errors in DNA replication
induced mutations
caused by mutagens which are agents that elevate the level of spontaneously occurring mutations
what does 5-bromouracil do to induce mutations
substitute for T, occasional faulty pairing w G
what does acridines, ethidium bromide (intercalative dyes) do to induce mutations
insert between 2 base pairs
what does radiation do to induce mutations
pyrimidine dimer formation
fermentation mutants
no longer able to use a specific carbon source
auxotrophs
mutants that are unable to synthesize a particular organic compound required for growth
cannot grow on defined minimal medium w/o some nutritional additive
antibiotic/bacteriophage mutant
mutants that have acquired resistance to common antibiotics or bacteriophage
virulence mutant
mutants that have LOST the ability to produce a virulence factor
replica plating is used to do what
detect auxotrophic mutants
transition vs transversion point mutation
transition -purine to purine etc
transervsion - purine to pyrimidine etc
conservative vs non-conservative missense mutation
conservative - same type/class mutation
ames test for mutagenicity use
used for screening potential carcinogens by testing for mutagenesis
used to test many chemicals
relies on observation that most common cause of cancer are mutations by DNA damage
(new mutations that reverse effect of og mutation)
