Identification of a distal control region by PCR dissection of GATA-1 promoter. (A) A map of construct G1-GM2 is shown. To generate deletion constructs, a specific primer (left arrowhead) and SP6 primer (right arrowhead) were used to amplify a portion of G1-GM2, as denoted by the broken line. (B) The percentages of GFP-positive 48-hour embryos obtained after microinjection of these constructs are shown, with the number of embryos observed for each construct indicated in parentheses.