Description:
<jats:p>A formal genetic analysis of the heterothallic, colonial green alga<jats:italic>Eudorina elegans</jats:italic>has been described. Wild-type strains were found to be sensitive to different drugs when grown on minimal agar containing very low concentrations of these drugs. Mutant strains resistant to high concentrations of drugs have been isolated. These are<jats:italic>msr-500</jats:italic>(resistant to 500 μg/ml of DL-methionine-DL-sulfoximine),<jats:italic>ery-r-100</jats:italic>(resistant to 100 μg/ml of erythromycin) and<jats:italic>sr-100</jats:italic>(resistant to 100 μg/ml of streptomycin). The wild-type phenotypes sensitive to these drugs have been designated as<jats:italic>mss-500</jats:italic>,<jats:italic>ery-s-100</jats:italic>and<jats:italic>ss-100</jats:italic>respectively. The<jats:italic>sr-100</jats:italic>also showed cross-resistance to other antibiotics belonging to the streptomycin group.</jats:p><jats:p>On genetic analysis, the<jats:italic>msr-500</jats:italic>and<jats:italic>ery-s-100</jats:italic>were found to be inherited in a Mendelian way. These alleles are not linked to each other or to the mating type locus. The inheritance of mating type was found to be due to a single gene difference.</jats:p><jats:p>The inheritance of<jats:italic>ss-100</jats:italic>/<jats:italic>sr-100</jats:italic>was found to be non-chromosomal and was characteristically uniparental, always transmitted through the female parent. The evidence for the non-chromosomal gene (NC genes) controlling<jats:italic>sr-100</jats:italic>/<jats:italic>ss-100</jats:italic>phenotypes in this organism has been derived from the exceptional zygotes in which the male parent apparently transmits streptomycin resistance to the progeny. Although ultraviolet or gamma-radiation resulted in normal survival curves of the exposed cells, no mutant deficient in any nutritional requirement was isolated.</jats:p>