Mutants at three luteus loci are defective in the conversion of protoporphyrin IX to Mg-protoporphyrin. These mutants have been localized to chromosome arms by crosses with TB testers. The l*-Blandy4 locus is uncovered by TB-1La, 5S8041 but not by TB-la in limited tests, therefore, it seems likely that this gene is located on the short arm of chromosome 5. The mutants l*-1040 and l*-1039 were located on the short arm of chromosome 10 with TB-10c. These are allelic to oy and have been renamed oy-1040 and oy-1039. The l*-Neuffer2 (E-59) locus is uncovered on 10L by TB-10(19). A four point testcross which localizes this gene between R and sr2 is presented in Table 1 (using the modified testcross system of D. S. Robertson, 1955, Genetics 40:746-760).

Table 1.

These data place the gene at 87 on the chromosome 10 linkage map (Figure 1). Since no stock of l2 is available and no other luteus mutants are located on chromosome 10L this mutant has been designated l13.

Figure 1.

The advice and helpful discussions of D. S. Robertson in the preceding studies are gratefully acknowledged.

Peter Mascia

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