Constructs, compositions and methods thereof having improved genome editing efficiency and specificity

Embodiments disclosed herein include novel nucleic acid-guided nucleases, novel guide nucleic acids, and novel targetable nuclease systems, and methods of use. In some embodiments, engineered non-naturally occurring nucleic acid-guided nucleases, can be used with known guide nucleic acids in a targetable nuclease system. In certain embodiments, targetable nuclease systems can be used to edit targeted genomes of humans and other species. In some embodiments, methods include, but are not limited to, recursive genetic engineering and trackable genetic engineering methods.