The genetics of some second chromosome melanotic tumour mutants ofDrosophila melanogaster

Abstract

SummaryThe genetic relationships of the available second chromosome melanotic tumour mutants in Drosophila melanogaster have been investigated. Complementation tests demonstrate the existence of new alleles of the tu bw locus and show that tu-W and tu-g are alleles. The data suggest that there is a minimum of three major gene loci on the second chromosome involved in tumorigenesis. A number of modifier genes were found which affect the penetrance of the major tumour genes analysed. These and the problems they cause in mapping the low penetrant tumour genes are discussed. It has not been possible to map tu-48a, tu- W and tu-g accurately, due largely to the presence of modifier genes. It appears that the genetic basis for melanotic tumour formation is complex.

Chromosomal assignment of the genetic factor, tu-91k, responsible for a melanotic tumour in the Drosophila melanogaster adult female

“…The 3rd chromosome and X chromosome are apparently not involved in the expression of the melanotic tumour development in the C-104 strain. It is possible that modifier loci are involved on other than the second chromosome, as the genetic control of other melanotic tumours has generally been found to be multifactorial (Barigozzi et al 1960;Burnet and Sang, 1964;Mampell, 1967;Lindsley and Grell, 1968;Belt and Burnet, 1972;Sparrow, 1974Sparrow, , 1978. It seems evident that the presence of a second chromosome from the C-104 strain alone is sufficient to induce melanotic tumour formation, since the proportion of flies carrying melanotic tumours among those homozygous for the second chromosome is not less than that in the original C-104 strain as reported in Kosuda (1990), although reduction in the phenotypic expression is usually expected in such crosses owing to changes in the genetic background.…”