GENETICS OF SORDARIA FIMICOLA. IX. LINKAGE GROUP II

Ten mutant sites have been located in linkage group II of Sordaria fimicola, nine of them affecting fertility. Two different regions of the chromosome are marked with allelic mutations or mutant sites in closely linked loci involved in sexual reproduction. Mutants of one of these two regions also have an arginine deficiency. Crosses between the self-sterile mutants of each region yield hybrid perithecia containing asci with four spores of each parental genotype and few or no asci with recombinant spores. The bearing that these findings have upon the evolution of heterothallism is discussed.     

GENETICS OF SORDARIA FIMICOLA. IV. LINKAGE GROUP I

El -Ani , Arif S., L. S. Olive , and Y. Kitani . (Columbia U., New York City.) Genetics of Sordaria fimicola. IV. Linkage group I. Amer. Jour. Bot. 48(8): 716–723. Illus. 1961.—A general technique for isolating and testing various morphological mutants induced by X ray is described. Eleven mutants differing in ascospore color, fertility, and rate and type of growth were studied in different crosses. This has led to the construction of the first linkage group in S. fimicola. The chromosome on which the 11 mutant loci occur is marked by a single locus on one arm and 10 on the opposite arm. The ascospore color mutant gray is autonomous, maintaining the mutant spore color in both homozygous and heterozygous asci, whereas milky, the other color mutant studied. expresses its mutant effect only in asci homozygous for the factor. Certain crosses involving 2 sterility mutants controlled by 2 non-allelic loci are fertile, and the progeny give rise to parentals as well as double-mutant and fertile recombinants.     

GENETICS OF SORDARIA FIMICOLA. III. CROSS-COMPATIBILITY AMONG SELF-FERTILE AND SELF-STERILE CULTURES

Carr , A. J. H. (Univ. Coll. Wales, Aberystwyth), and Lindsay S. Olive . Genetics of Sordaria fimicola. III. Cross compatibility among self-fertile and self-sterile cultures. Amer. Jour. Bot. 46(2) : 81-91. Illis. 1959.—Cross-compatibility in Sordaria fimicola is shown to be dependent upon a number of factors controlling the sexual process, from hyphal anastomosis and nuclear migration on through to perithecial formation and nuclear compatibility. Fertile cultures which were incompatible through inability to anastomose were induced to cross by the use of a third culture which would anastomose with both. Certain spontaneous or irradiation-produced sterility mutants were found to be compatible if the sterility genes were at different loci, through complementation by the wild-type alleles. In some pairings, cross-karyogamy was preferential, and in one case, only hybrid perithecia were produced. Fully fertile recombinants segregated from these crosses in frequencies which indicated that the sterility loci were unlinked. Certain sterility genes were found to influence hyphal anastomosis, nuclear migration, and the development of fertile sector heterokaryons from the zone of anastomosis. Mutant factors at two loci in a U.V. mutant causing self-sterility were found also to be responsible for lethality in ascospore germination. Factors in one sterility mutant controlled the production of a sterility-inducing substance which diffused into the medium. In some crosses, complementation of two sterile cultures towards fertility is shown to require a balanced nuclear ratio. Factors are described which increase the inhibitory effect of one sterility gene, while another factor was found to suppress its effect and thereby make the culture self-fertile. It is concluded that, since there is recombination between the sterility loci, these results do not represent the derivation of balanced heterothallism from a normally homothallic system, although it may lead by evolutionary progression to such a life cycle. The possible physiologic action of the sterility genes is discussed.     

我国东北地区3个群体DYS390多态位点的遗传学研究

目的　研究中国群体Y染色体微卫星位点 DYS390遗传多态性 ,可以用于追溯人类进化上的父系祖先 ,也可以为人类基因组和法医学等研究积累数据。方法　采用 PCR技术扩增微卫星DNA片段 ,再经变性凝胶电泳及银染方法 ,对我国东北地区汉族、蒙古族及朝鲜族 3个群体的1 0 2例男性个体的 DYS390位点的遗传多态性进行了研究。结果　除汉族群体发现 5种等位基因外 ,朝鲜族和蒙古族群体均检出 4种。在汉族群体中 ,我们检出 1例具223bp等位基因。等位基因频率分布在汉族、朝鲜族以211bp的频率为最高 ,分别为0.439和0.451 ;而蒙古族群体则以215bp的频率为最高 (0.433)。结论　 3个群体之间 DYS390位点等位基因频率无显著性差异 ( Fisher精确概率检验 :P=0.930 )。 3个群体中DYS390位点 5种等位基因的分化程度以223bp为最高 ,分化程度最低的为211bp。聚类分析表明3个群体的父系亲缘关系较为密切 ,其中以汉族与朝鲜族之间的遗传距离最近。     

THE PHYSIOLOGICAL BASIS OF NATURAL SELECTION AT THE LAP LOCUS

An extensive research program was undertaken to evaluate the contribution of genetic variation at the Lap locus to variation in physiological traits under natural conditions. Rates of carbon and nitrogen metabolism were monitored in a population of the mussel Mytilus edulis near the center of the Lap allele frequency cline on the north shore of Long Island. The goal of this research was to establish whether the previously described genotype-dependent differences in physiological phenotype are meaningful in ecologically relevant circumstances. It was predicted from laboratory studies that, in nature, genotype-dependent differences will exist for rates of nitrogen excretion and that other aspects of the animal's physiology, particularly rates of carbon metabolism, will be unaffected by Lap genotype. Rates of amino acid and ammonia excretion were significantly dependent upon Lap genotype; individuals with the Lap⁹⁴ allele exhibited greater rates of nitrogen loss. These differences among genotypes were most evident in the fall, between September and December. The genotype-dependent component of rates of nitrogen loss were also largest relative to the total rate of excretion during the fall period. As predicted, other aspects of the nitrogen metabolism (acquisition) and rates of carbon metabolism were independent of Lap genotype. There was a striking congruity among a variety of observations that all indicate that phenotypic differences in nitrogen metabolism are the basis of natural selection at the Lap locus in Long Island Sound. Rates of growth were minimal during the fall months (Hilbish, 1985) and mussels are known to lose weight in a genotype-specific manner during this period (Koehn et al., 1980). Rates of elemental gain and loss were summed to produce carbon and nitrogen budgets; these data show the fall to be a period of extended deficit in carbon and nitrogen balance. Genotype-dependent losses of ammonia and amino acids were greatest during the fall months. Finally, selection against the Lap⁹⁴ allele occurs predominantly in the fall (Hilbish, 1985). The data indicate that the depletion of nitrogen resources provides the basis for selection against Lap⁹⁴ genotypes during the fall months.