Restriction sites, or restriction recognition sites, are specific sequences of nucleotides that are recognized by restricting enzymes. The sites are generally palindromic, (because restriction enzymes usually bind as homodimers) and a particular enzyme may cut between two nucleotides within its recognition site, or somewhere nearby. For example, the common restriction enzyme EcoRI recognizes the sequence GAATTC and cuts between the G and the A on both the top and bottom strands, leaving an overhang (an end-portion of a DNA strand with no attached complement) on each end, of AATT. This overhang can then be used to ligate in (see DNA ligase) a piece of DNA with a complementary overhang (another EcoRI-cut piece, for example).