Molecular cloning
Cutting, joining, and propagating DNA hasn't gotten less fiddly. It's just gotten more standardized. Restriction digestion and ligation still anchor most subcloning workflows, backed by end-modification enzymes for blunting and dephosphorylation and a competent-cell strain matched to what you're transforming.
Digest
Cut vector and insert with Type II restriction endonucleases at compatible sites, check methylation sensitivity (dam/dcm) and star-activity conditions on the datasheet before you scale a digest up.
Prep the ends
Blunt sticky overhangs, dephosphorylate a linearized vector to suppress self-ligation, or phosphorylate an insert with a polynucleotide kinase, the end-modification step that keeps background colonies down.
Ligate
Join insert to vector with an ATP-dependent DNA ligase, sticky-end ligations run fast at room temperature, blunt-end ligations need higher enzyme concentration and longer incubation (or 16 °C overnight).
Transform & screen
Transform the ligation into a chemically competent cloning strain, then screen colonies by colony PCR or diagnostic restriction digest before you commit to a maxiprep and sequencing.
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Type IIP or Type IIS restriction enzyme?
Type IIP enzymes cut within (or symmetrically around) a fixed palindromic recognition site, the default for conventional restriction cloning. Type IIS enzymes cut outside an asymmetric recognition site at a defined distance, which is what makes scarless Golden Gate / MoClo assembly possible: the recognition site is removed from the final construct.
Why does dam/dcm methylation matter?
Most cloning strains (including standard DH5-alpha) methylate DNA at dam (GATC) and dcm (CCWGG) sites. Some restriction enzymes are blocked by overlapping methylation, check the datasheet if a digest silently fails on plasmid prepped from a methylation-positive strain, and consider a dam-/dcm- strain if you need those sites cut cleanly.
Chemically competent or electrocompetent?
Chemically competent cells (heat-shock transformation) are simpler and sufficient for routine ligations and re-transformation of intact plasmid. Electrocompetent cells give 10–100× higher efficiency, which matters for large ligations, large libraries, or DNA that transforms poorly by heat shock.
Which competent-cell strain do I actually want?
A general cloning strain (recA-, endA-) like DH5-alpha or the 10-beta family gives clean, stable plasmid prep for routine subcloning. Reserve a λDE3 lysogen (BL21(DE3), BL21(DE3)pLysS) for protein expression. It carries the T7 RNA polymerase these cloning strains lack.
More application workflows, curated products, and category links live on the applications hub. Datasheets, SDS, and Certificates of Analysis are under Documents.