of the codons gct gat gag ttt ggt cat att aag atg aat cct cag cgt tct act gtt tgg tat this diversity is shown in the context of a synthetic 3 23 gene in table 18p the diversity oligonucleotide on is synthesized from bspei to bstxi and can be incorporated either by pcr synthesis using overlapping ons or introduced by ligation of bspei bstxi cut fragments table 22p shows ons that embody the specified variegation pcr using on r1v1vg on r1top and on r1bot gives a dsdna product of 73 base pairs cleavage with bspei and bstxi trims 11 and 13 bases from the ends and provides cohesive ends that can be ligated to similarly cut vector having the synthetic 3 23 domain shown in table 18p replacement of on r1v1vg with either onr1v2vg or onr1v3vg allows synthesis of the two alternative diversity patterns given below alternatively one can include cdr1s of length 7 and or 14 for length 7 a preferred diversity is s t 1 s g x 2 s g x 3 y 4 y 5 w 6 s g x 7 seq id no 107 where s t indicates an equimolar mixture of ser and thr.