Worm Breeder's Gazette 3(2): 23
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We have identified eight genes that can mutate to give a fertilization-defective (FER) phenotype due to defective sperm. Our mutants are all recessive, but because of their effect on sperm we asked if both classes of sperm produced in a heterozygote were equally fertile. Heterozygous males, grown permissively or restrictively, were mated to their corresponding sterile hermaphrodites. The genotype of the progeny of such crosses was then determined by placing them on plates containing 1.5 mM Tramisol. The animals are paralyzed within minutes and expel the contents of their uterus revealing whether they are sterile or fertile. In some cases, closely linked UNC or DPY markers were used to identify progeny fertilized by sperm bearing the fer chromosome. The results are presented in the table as the fraction of progeny fertilized by a fer sperm (the transmission ratio). [See Figure 1] As shown, hc1 and hc3 have the 0.5 ratio expected from Mendelian principles. However, sperm bearing the hc4 and hc34 mutations have reduced fertility. For hc34 the effect is temperature sensitive. For hc4, it is less so, which may reflect the fact that the phenotype is partially defective at 16 C. We have examined the sperm from the hc4/+ males with the scanning electron microscope and find there are two classes of sperm, one of which is indistinguishable from wild-type. This observation, together with the observation that homozygous mutant males make sperm in normal number and transfer them to hermaphrodites, makes it unlikely that the cause of the reduced transmission of mutant bearing sperm is due to sperm death or degeneration. These results show that the hc4 and hc34 mutations are expressed autonomously in the sperm and that gene expression must continue after the first reductive division in meiosis in order to cause a defect in the sperm bearing the mutant allele.