Question

In your experiment today, you transformed pcDNA3 into E. coli DH5a cells. Name TWO other types of E coli strains that may be used for genetic transformations and describe the advantages of these stains when compared to DH5a?

Answer 1

pcDNA3 is a vector with 5446 base pairs, has a Geneticin selectable marker and a reverse-orientation multiple cloning site. It is a mammalian expression vector with CMV promoter.

Two other types of E. coli strains other than DH5a cells can be DH10B and BL21 (DE3) . DH10B is commonly used across the research community, and has advantages that include high transformation efficiency, the ability to take up and stably maintain large plasmids, the lack of methylation-dependent restriction systems (MDRS), and colony screening via lacZ-based α-complementation. DH10B strain  aid in plasmid stability and improved the quality of prepared plasmid DNA because they carry recA1 and endA1 mutations. BL21 (DE3) is used for T7 expression, can be used for antibiotics for plasmid selection.BL21 lack the lon and ompT proteases hence gives stability of recombinant proteins. It is used  for high-level gene expression and production of recombinant proteins in bacterial systems.