BioBrick parts are functional DNA sequences that are flanked by a set of restriction sites called prefix and suffix. These compatible restriction sites makes it possible to efficiently assemble different parts to build biological circuits.
Figure 1: The BioBrick prefix and suffix contain specific restriction sites that allow for Lego-brick like assembly of many parts.
Assembly of BioBricks is usually performed using the 3A Assembly method. The assembly of two parts results in a cloning scar between the two initial parts and yeilds a new BioBrick containing the two parts flanked by the prefix and suffix.
Figure 2: Ligation of the overhangs produced by SpeI and XbaI digestion results in a cloning scar that cannot be cut by any of the two restriction enzymes.