mutations in e coli genome for better transformation Flashcards
K12
strain of E coli originally taken from a stool sample in 1922
F-
the original K12 strain had a fertility plasmid (F episome) ~100kb in size & used for conjugation, it was subsequently removed
Φ80lacZΔM15
an integrated virus carrying a transgene encoding the omega (big) fragment of lacZ (B-galactosidase)
Δ(lacZYA-argF)
a deletion of the whole lac operon and argF which is used in
arginine biosynthesis,
but is a gene duplication so is redundant
recA1
a gene used in DNA repair in E.coli through the process of homologous recombination, it will cause repeated sequences in plasmids to get deleted
endA1
a mutation in DNA endonuclease I, a protein which degrades DNA in plasmid preparations–makes it non functional
hsdR17
a mutation of the EcoK1 restriction/modification system to prevent the endonuclease from cutting unmethylated 5’- AACN6GTGC-3’
phoA
defective for a component of the
periplasmic alkaline phosphatase – rarely useful
supE44
amber suppressor - encodes a tRNA for the UAG stop codon and inserts glutamine instead
λ–
lacking an integrated lambda prophage, the original strain had a lambda infection but was subsequently cured, allows for transformation with lambda for large inserts, library formation
thi-1
auxotrophic for thiamine, so it must be grown on complete media, or a minimal media with supplied thiamine
gyrA96
mutation in DNA gyrase, leaves gyrase functional and resistant to nalidixic acid
relA1
RNA synthesis can continue uncoupled to protein synthesis, such as when translation is stopped by antibiotics
Lac Iq
a constitutive repressor of the lac operon, shuts down expression from lac promoter unless IPTG is added to the media
DE3
encodes a T7 RNA polymerase, useful as some expression vectors use a T7 promoter for expression
