Terminal non-homologies indicate an underlying asymmetry. (A) The substrates are illustrated showing the location of the 50 bp homology arms (red), hydroxylated (O) or phosphorylated (P) 5' ends and the additional non-homology (30 bp) on one end or the other. OP5' refers to the addition of the non-homology onto the 5' end of the LSP. OP3' refers to the addition of the non-homology on the 3' end of the LSP. (B) Results using the substrates shown in (A) after recombination into a BAC in the presence of Redαβγ. (C) The same assay as in (B) except that the homology arms of the PO substrate (50 50) were altered to be shorter on the 5' end of the LSP (30 50), the 3' end (50 30) or both (30 30).