DNA sequence of the 5′ region of the β-globin gene in the Asian Indian family. The individuals I1, I2, II1, II2, and II3 (as in Fig 4) are represented by lanes 1, 2, 3, 4, and 5, respectively. The termination reactions are loaded in consecutive lanes in a block, ddGTP (G), ddATP (A), ddTTP (T), and ddCTP (C). (a) The 5′ breakpoint of the crossover region is located in the region of the (AT)_xT_y repeats; (b) the 3′ breakpoint is located at the G/T polymorphic site at position +568 (arrowed).