Kanamycin (Kan)
An antibiotic that inhibits protein synthesis by binding to the 30s ribosomal subunit and preventing translocation. KanR is usually due to a cytoplasmic aminoglycoside phosphotransferase that inactivates kanamycin by covalently phosphorylating it. Because kanamycin rapidly inhibits protein synthesis, when cells acquire the kanR gene phenotypic expression is required before the cells become kanamycin resistant.

Kilobase (Kb or Kbp)
1000 nucleotides of DNA or RNA.

Kinase
An enzyme that transfers phosphate from ATP to another molecule.

Klenow fragment
A proteolytic fragment of DNA polymerase I that contains the DNA polymerase activity and the 3' to 5' proofreading activity but lacks the 5' to 3' exonuclease activity. This enzyme is widely used for DNA sequencing.