LINKAGE STUDIES IN<i>TRIBOLIUM CONFUSUM</i>DUVAL. II. THE MAP POSITION OF THREE HOMEOTIC MUTANTS.

Abstract

In the first paper of this series (Soltoloff, 1964) the literature on the genetics of TriboLiz~77z CO~~~ZLSZL~~ was reviewed, seven new autosomal mutations were described and linltage relationships between some of these genes established. Since then, Soltoloff (1966) has given some preliminary information on some 50 different mutations of spontaneous occurrence of which 11 are sexlinked and the remaining autosomal. Dawson (1966) and Weber and Roberts (1966) have contributed further linkage information. The purpose of the present paper is to add some information on the map position of three homeotic genes. Such studies have intrinsic interest since the penetic information available for the Coleo~tera is verv limited. The interest e I 1s enhanced by the results of the comparative cytology of T. casta7zezm?, T. CO~~~ZLSZL~JZ and T. destrz~ctor. Smith (1952) concludes that T. crrstanez~7n, with chromosomal formula 9AA + X + y, represents the most primitive species. The ltaryotype of T. co72fusz~nz is 8AA + X + Y. The X and Y are larger, referred to as neo-X and neo-Y. and a~~arentlv derived from a casta72ezn/il-lilte 11 J ltaryotype by the translocation of an autosomal pair to the X and Y. In T. destrz~cto~, also with 8AA + X f Y, the autosomal portion of the neo-X and neo-Y apparently has been discarded. During the formation of the neo-Y there has been heterochromatinization with the Gsult that genes associated wit11 the Y could, and apparently have, become inert. Hence, Smith (1950, 1952) has postulated that some genes behaving in an autosomal fashion in T. castanezmz will be found to be ses-linltcd in T. coil1fZ~sz~iln. The data presented in this paper are of interest because, among homeotic mutants in Insecta, the ones described here appear to be the only ones inherited in sex-linltcd fashion. Therefore, they have some bearing on Smith's hypothesis.