EXAM 3 P5 Flashcards
exchange of bacterial genetic information
new genes can be acquired during their lifetime, usually only small amounts of DNA not whole genomes
plasmids
pieces of DNA (extrachromosomal genetic elements) and generally circular
smaller than the chromosome
have their own origin of replication using the cells normal DNA replication machinery
often called multi copy plasmids since there are multiple per cell
not essential for cell survival
plasmid function
provide the cell with something positive by expanding metabolic ability
can express conjugation, provide metabolic function, antibiotic production, resistance, and virulence
essential tools in all molecular biology labs
homologous recombination
new DNA that comes in is a plasma with its own origin of replication and can replicate past the progeny cells
if the DNA lacks an origin, and is not passed on to part of the genome, it must find another way
recombination requires 2 molecules have an extended region of sequence similarity
recA proteins
bind ssDNA and initiates the process of homologous recombination
takes the ssDNA and scans across the other dsDNA and finds homologous regions, aligns them, and initiates recombination
horizontal gene transfer
transfer from one unrelated cell to another
conjugation, transformation, and transduction
vertical gene transfer
gene transfer to your progeny
donor cell/strain
origin of the DNA to be transferred
recipient cell/strain
cell receiving the new DNA
recombinant cell/strain
result if the stability maintains the incoming DNA
about 99% recipient, only a small bit is transferred
DNase
an enzyme that destroys DNA
Griffith
discover the transforming principle in the 1920s
did experiments looking at the ability of streptococcus to cause disease in mice
type 1 was smooth and 2 was rough. if 1 was injected into the mice, they died. 1 had a “smooth” capsule material. if he took 1 and killed the capsule, the mice lived. if 2 were injected they lived. he combined both living factors for injection and the mice died. something in the dead smooth cells was transforming the rough cells into smooth cells.
Avery, Macleod, and McCarty
in the 1940s, they purified DNA and showed the process Griffith performed was DNase sensitive
provided the first direct evidence that DNA is the genetic material
competent
able to be transformed, they bind, uptake, and recombine DNA
natural transformation
species can naturally become competent. they have a set of genes allowing them to find DNA in the environment, transfer it to the cell, and recombine it into their.
dsDNA is bound to a cell surface
easier to pick up ssDNA than dsDNA
artificial (chemical) transformation
forces competence no genes or cellular energy required not an active process of the cells dsDNA enters the cell treats the cells with salts, detergents, chemicals, forming holes in the mem and disrupting it. kill about 90% of the cells
electroporation
suspends the cells in a solution and pasteur it with a high voltage of electric shock, depolarizing the mem, ridding it of negative charges so DNA can get through
transduction
cell gets infected with a virus and while reproducing the virus accidentally packages some of the host cell DNA instead of the viral DNA. the products look and act like viruses, but carry non-viral DNA, which can get injected into a recipient cell
lytic cycle
breaks down host DNA with its small bits, sometimes making mistakes
phage lysate
contains many phage particles and some transducing particles
transducing particle
can still bind another host cell and inject its DNA into the cell
P22 phage
infects salmonella
P1 phage
infects e. coli
conjugation
DNA transfer from direct cell-cell contact
almost always encoded on a plasmid
requires an origin of transfer (ori T)
2 origins are on the plasmid
not DNase sensitive since DNA is never exposed to the environment
tra genes
produce a set of tra proteins, which are the apparatus that allow the process of conjugation
F+
potential donor
has a plasmid
F-
potential recipient
F pilus
pulls cells together during conjugation to form a mating pair
chromosome mobilization
results from the formation of Hfr strains
integrated F plasmid cell
still expressed tra gene, makes a pilus, and initiates DNA transfer at ori T
recipient
can recombine homologous regions of incoming chromosomal DNA
never gets the whole F plasmid sequence
does not become F+
