Sticky and blunt ends (nonfiction)
DNA ends refer to the properties of the end of DNA molecules, which may be sticky ends (cohesive ends), blunt ends or in other forms. The concept is used in molecular biology, especially in cloning or when subcloning inserts DNA into vector DNA. Such ends may be generated by restriction enzymes that cut the DNA – a staggered cut generates two sticky ends, while a straight cut generate blunt ends.
A sticky or cohesive end has protruding single-stranded strands with unpaired nucleotides called overhangs, each overhang can anneal with another complementary one to form base pairs. The two complementary cohesive ends of DNA can anneal together via hydrogen bonding, the stability of these paired ends depends on the melting temperature of the paired overhangs. DNA ligase can join two adjacent strands of DNA by forming a covalent bond between the sugar-phosphate moieties of adjacent nucleotides to join the two together via a phosphodiester bond in a process called ligation. The blunt ends however do not have such protruding strands, and therefore cannot anneal together, and consequently ligation between blunt ends is less efficient.