Sticky and blunt ends

DNA ends refer to the properties of the ends of linear DNA molecules, which in molecular biology are described as "sticky" or "blunt" based on the shape of the complementary strands at the terminus.

Here is an example of a small piece of blunt-ended DNA: Non-blunt ends are created by various overhangs.

These ends are called cohesive since they are easily joined back together by a ligase.

Since the overhangs have to be complementary in order for the ligase to work, the two molecules can only join in one orientation.

Two nucleotide sequences which correspond to each other in this manner are referred to as complementary: A frayed end refers to a region of a double stranded (or other multi-stranded) DNA molecule near the end with a significant proportion of non-complementary sequences; that is, a sequence where nucleotides on the adjacent strands do not match up correctly: The term "frayed" is used because the incorrectly matched nucleotides tend to avoid bonding, thus appearing similar to the strands in a fraying piece of rope.

Although non-complementary sequences are also possible in the middle of double stranded DNA, mismatched regions away from the ends are not referred to as "frayed".

Ronald W. Davis first discovered sticky ends as the product of the action of EcoRI, the restriction endonuclease.

Free energy approximations can be made for different sequences from data related to oligonucleotide UV thermal denaturation curves.

[6] Also predictions from molecular dynamics simulations show that some sticky end links are much stronger in stretch than the others.