Sex and Crossing over in Linkage Group IV of TRIBOLIUM CASTANEUM.

HE formal genetics of flour beetles of the genus Tribolium is still in its infancy. Although these organisms have found a habitat in the laboratories of the ecologist, the quantitative geneticist, and more recently, the population biologist (KING and DAWSON 1972) their use has been restricted by the availability of only a limited number of reliable mutants and further hampered by a meager knowledge of linkage relationships. At present there are 10 linkage groups corresponding to the 10 chromosomes of T. castaneum, the most widely used and genetically best known of the species in this genus. Although some of the linkage groups are represented by only a single gene, linkage group IV is one of the better marked, with some 11 loci that have been at least tentatively mapped ( SOKOLOFF 1966; SOKOLOFF, HOY and JOHNSON 1966; DAWSON 1972). One interesting feature associated with linkage group IV is a sex difference in the frequency of crossing over. SOKOLOFF (1963) reported no sex difference in a study of crossing over between two loci on this chromosome, but JOHNSON (1966) found a significant difference for the same two loci. During the course of studies with a new mutant in this linkage group, further information was collected on the sex difference in crossing over.