EXTRACHROMOSOMAL ELEMENT DELTA IN <i>DROSOPHILA MELANOGASTER</i>

Abstract

The extrachromosomal element denoted by delta was discovered first in bwD/bwD strain owing to its nature of producing a segregation distortion in the mating of females of this strain with certain Cy heterozygous males (Minamori 1969). The distortion was interpreted to be due to differential mortality of zygotes; namely the bwD heterozygotes for a special second chromosome, denoted as sensitive chromosome, may be killed by delta more frequently than Cy/bwD heterozygotes. There were two kinds of sensitive chromosomes. Some sensitive chromosomes (e. g. bwD, S-5, S-7, S-9 chromosome; Minamori 1969) allowed the multiplication of delta more in homozygous condition and less in heterozygous condition, hence, they were assumed to carry a semidominant gene(s) which allows the multiplication. These chromosome lines have stably retained delta since they were discovered in 1965. The segregation distortion was always observed in the reciprocal matings between any two of these sensitive lines. On the other hand, in other sensitive lines (e. g. Pm chromosome, Minamori 1969; S-Cy chromosome; un

Hybrid Dysgenesis in Drosophila melanogaster

“…The delayed effect of genotype and temperature changes bears striking analogies to those occurring for the extrachromosomal element delta studied by Minamori (27) and others. However, a common basis for the two systems seems excluded by the available data.…”

“…Confusion can be caused by I-R or P-M interactions in studies of independent genetic factors also producing dysgenic traits. This may be the case for the extrachromosomal element delta (27,51) and perhaps also the segregation distorter system (52) although the latter seems to be genetically different from both I-R and P-M systems and is, therefore, less confusing. In any case, the knowledge of the P-M and I-R classifications of the stocks used is essential to exclude the possibility that some experimental results might be produced by several interactions.…”

Malignant Neoplasms of Genetic Origin in Drosophila melanogaster

“…It would be of great interest to determine their viral nature. They may possess regulatory gene functions, and may be responsible for genetic instability and certain types of mutations (21,49). Drosophila is easy and inexpensive to rear in the laboratory and has a short generation time (11 to 12 days at 25°C).…”

Further Analysis of Hybrid Dysgenesis in Drosophila melanogaster

“…The hypothesis that dysgenesis is caused by genetic elements which are inserted in the chromosomes of one of the strains interacting to produce the phenomenon has been suggested by a number of authors (Minamori 1971;Green 1977;Slatko 1978). Indeed, it has recently been shown that P-M dysgenesis is associated with a DNA sequence called the P factor which is found in multiple copies in the chromosomes of P strains but which is absent from the chromosomes of M strains (Bingham et al, personal communication).…”