Abstract
A Drosophila melanogaster stock carrying an EMS-treated third chromosome (5A) over a balanced lethal chromosome (TM6) was analysed. Homozygous 5A males and females both had rudimentary gonads. Genetic analyses of the stock revealed that two mutations are present which are responsible for the gonadal dysgenesis; ms(3)m15A acting on the germ cells and producing the rudimentary testes and fs(3)f15A affecting the ovarian mesodermal cells and causing rudimentary ovaries. These mutations are located near the proximal heterochromatic region of the third chromosome. In addition, two more sterility mutations were found on the same chromosome; fs(3)f25A which produces maternal-effect embryonic lethality, and ms(3)m25A which blocks the maturation of spermatids. A second chromosomal gene, su(m15A), was identified which specifically suppresses the action of ms(3)m15A.
