79
 16, the loss of an Mspl site in this region (at approximately 2785bp) could

 explain the presence of the 0.62kb fragment in these two variants.

 Digestion of the 1.9kb region from Hindlll to BgAl (178HB) with Mspl

 produced fragments of approximately 1.3kb, 0.42kb, 100bp and 70bp. Mspl

 sites were identified near the Hindlll and Bg/l sites in subclone pG178HB

 (Figure 13). Mspl restriction fragments to which 178HB hybridized are shown

 in Figure 17. The Mspl restriction fragment pattern of 178HB corresponded to

 variant M103: two site polymorphisms are indicated in Figure 17 that could

 account for the fragments detected by 178HB in two other variants.

 Digestion of the 2.0kb Bgll EcoRI4 fragment (178BE4) with Mspl

produced fragments of approximately 1.4kb, 0.33kb, and 0.25kb (Figure 13).

The Mspl fragments to which 178BE4 hybridized in Southern blots are shown

in Figure 18: these included combinations of approximately 1.8kb, 1.4kb,

1.25kb, 0.77kb, 0.56kb, and 0.35kb fragments. The loss of an Mspl site in

the 178HB region (Figures 13 & 17, at approximately 5420bp) could account

for the 0.77kb fragment detected in variants M101 and M302, and for the

detection of this fragment with both 178HB and 178BE4. Since 178BE4

hybridized to more Mspl fragments than had been found in the digestion of the

insert and accounted for by overlapping with adjacent regions, the placement

of Mspl sites within 178BE4 was based on double digests with Spel, Sphl, Nsil,

and Sa/i, and the results of the hybridizations of 178HB, 178BE4, and 178E4P2

(following).