Bio-Rad Ligation and Transformation Module - Manual (Page 18)

Chemical structure of deoxyribose sugar and deoxyribose nucleic acid (DNA).
Ligation is used to join vector DNA and insert DNA. There are two ways in
which DNA can be ligated into a cloning vector, one using DNA with
so-called sticky ends and the other using DNA with blunt ends. Unlike DNA
with blunt ends, DNA with sticky ends has one or more unpaired bases at
its ends that do not have complementary bases on the other strand of the
double helix. When a DNA fragment is generated by
Taq DNA polymerase
by a process like PCR, it typically has sticky ends with a single adenosine
(A). When a DNA fragment is generated by cutting a piece of DNA with a
restriction enzyme (an enzyme that cuts both strands of double-stranded
DNA), it may have either sticky ends or blunt ends, depending on the
restriction enzyme.
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