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At least 19 recordsLinked to original sources
PubMed1978

F- mating materials able to generate a mating signal in mating with HfrH dnaB(Ts) cells.

The purified outer membrane from F- (W1-3) cells was shown to inhibit mating effectively, but the purified cytoplasmic (inner) membrane did not. These membranes, heat-treated minicells, and ultraviolet-irradiated minicells were examined for their ability to generate a mating signal at 43 degrees C in mating with HfrH dnaB(Ts) cells. The outer and inner membranes and heat-treated minicells all failed to stimulate incorporation of radioactive thymine; only ultraviolet-irradiated minicells retained the ability to generate a mating signal for the donor to initiate transfer replication.

Cell Membrane↗
PubMed1976

Effect of 1,10-phenanthroline on bacterial conjugation in Escherichia coli K-12: inhibition of maturation from preliminary mates into effective mates.

The addition of 1 mM orthophenanthroline (OP) into a mating mixture drastically reduced the production of recombinants. Examination of the effect of OP on each step of conjugation showed that the effect on the following steps could not account for the up to 500-fold reduction of recombinant formation: (i) preliminary mate formation and (ii) deoxyribonucleic acid transfer and integration. Taking these results and additional experiments together, we conclude that OP inhibits the maturation of preliminary mates into effective mates. Kinetic experiments showed that there were two phases in the maturation of preliminary (OP-sensitive) mates into effective (OP-resistant) mates. The half-time (the time required to reach 50% OP-resistant mates) was 2.5 min for the first phase and 4 min for the second phase, with an overall half-time of 7.5 min. In contrast, only 3 min was required to reach 50% Zn2+-resistant mates. The difference in half-time suggests that there is an intermediate step involved to form an effective mate from a preliminary mate.

Cations, Divalent↗
PubMed1975

Mating type and sporulation in yeast. I. Mutations which alter mating-type control over sporulation.

In Saccharomyces cerevisiae, meiosis and spore formation as well as mating are controlled by mating-type genes. Diploids heterozygous for mating type (aalpha) can sporulate but cannot mate; homozygous aa and alpha-alpha diploids can mate, but cannot sporulate. From an alpha-alpha diploid parental strain, we have isolated mutants which have gained the ability to sporulate. Those mutants which continue to mate as alpha-alpha cells have been designated CSP (control of sporulation). Upon sporulation, CSP mutants yield asci containing 4alpha spores. The mutant gene which allows alpha-alpha cells to sporulate is unlinked to the mating-type locus and also acts to permit sporulation in aa diploid cells. Segregation data from crosses between mutant alpha-alpha and wild-type aa diploids and vice versa indicate (for all but one mutant) that the mutation which allows constitutive sporulation (CSP) is dominant over the wild-type allele. Some of the CSP mutants are temperature-sensitive, sporulating at 32 degrees, but not at 23 degrees. In addition to CSP mutants, our mutagenesis and screening procedure led to the isolation of mutants which sporulate by virtue of a change in the mating-type locus itself, resulting in loss of ability to mate.

Cell Nucleus↗
PubMed1975

The mating reaction in yeast. I. A new mutation involved in the determination of mating-type.

The isolation and preliminary characterisation of a mutation, not linked to the mating type locus, but which apparently alters the mating type directed sequence of events during sexual conjugation is described. Haploids of the alpha mating type carrying this gene will now mate with other alpha haploids, creating diploids homozygous for the alpha mating type locus. This gene can be carried, but not expressed, in a haploids, however in a/alpha diploids homozygous for this gene mating is now possible with both a and alpha haploids giving either a/a/alpha or a/alpha/alpha triploids. Using these strains mating-deficient mutants have been isolated and preliminary results on their characterisation presented.

Conjugation, Genetic↗
PubMed1977

Parental investment, mate choice, and mate quality.

Current theory in sexual selection is extended to predict within-sex variability with regard to selectivity towards mates in different mating systems. Generally, the sex that invests more in the care of each offspring should be more selective of mates than the sex investing less. Within each sex, individuals of low male quality should be less selective than individuals of high quality, but there should be less variation in selectivity among individuals of the sex investing more. When only one sex contributes parental care, however, individuals of that sex should be uniformly selective, while the other sex is expected to mate indiscriminately. Using feral pigeons (Columba livia), these hypotheses are tested for the case in which both sexes contribute substantial parental care, but in which females contribute more than males. As predicted, females were found to be more selective of mates than males were. On certain criteria, males of lower quality were less selective of mates than males of higher quality.

Animals↗
PubMed1979

A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci.

A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S. cerevisiae. This suppressor, sir1-1, restores mating ability to mat alpha 1 and mat alpha 2 mutants and restores sporulation ability to mat alpha 2 and mata1 mutants. MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to alpha-factor, both properties of a/alpha diploids. Furthermore, sir1-1 allows MATa/MATa, mat alpha 1/mat alpha/, and MAT alpha/MAT alpha strains to sporulate efficiently. All actions of sir1-1 are recessive to SIR1. The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed. The ability of sir1-1 to suppress the mat alpha 1-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to alpha. Thus, as predicted by the cassette model, HMa is functionally equivalent to MAT alpha since it supplies functions of MAT alpha. We propose that sir1-1 is defective in a function. Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HM alpha.

Chromosome Mapping↗
PubMed1977

Degradation of mating factor by alpha-mating type cells of Saccharomyces cerevisiae.

The change of the mating factor activity during the culture of Saccharomyces cerevisiae X-2180 1B, an alpha-mating type haploid strain, were followed. The activity increased rapidly during the exponential phase of growth, reached a maximum during the early stationary phase and then decreased. Oligopeptides comprising partial sequences of the mating factor were isolated from the culture fluids at various phases of cell growth. We concluded that the mating factor, a tridecapeptide, was degraded during culture into two peptides, Trp-His-Trp-Leu-Gln-Leu and Lys-Pro-Gly-Gln-Pro-Met-Tyr, by cleavage of the peptide bond between Leu-6 and Lys-7 of the mating factor. A dodecapeptide lacking the N-terminal Trp residue was not detected at any stage of cell growth examined.

Amino Acid Sequence↗
PubMed1979

Purification and partial characterization of a factor, a mating hormone produced by mating-type-a cells from Saccharomyces cerevisiae.

Cells of Saccharomyces cerevisiae exhibiting the a mating type secrete into the culture medium a mating-type-specific hormone activity (a factor), which specifically causes a transient arrest of DNA replication and cell division in cells of the opposite mating type, alpha. Three compounds exhibiting a factor activity have been found in culture filtrates from a cells. The most active compound has been purified more than 10(5)-fold and appears to be homogeneous on the basis of thin-layer chromatography and thin-layer electrophoresis in different systems. We propose that this compound, which exhibits in alpha cells the biological activities that have been attributed to a factor, represents pure a factor. a factor has been characterized as a very hydrophobic undecapeptide with the following amino acid composition: H2N-Tyr (Asx1, Gly1, Ala1, Val1, Ile2, Phe1, Lys1, Trp1, Pro1). Although in their respective target cells the biological effects of a factor and of alpha factor, the corresponding mating hormone of mating-type-alpha cells, are remarkably similar, the primary structures of both hormones appear to be quite different.

Agglutination↗
PubMed1975

The mating reaction in yeast. II. Spontaneous occurrence of omni-mating types.

Meiosis in diploids of Saccharomyces cerevisiae either homozygous or heterozygous for the dmt gene result, in about 5% of the meiotic products, in spores which have undergone an interconversion at the mating-type locus. Some of these interconversions appear to be the result in the generation of spontaneous omni-mating strains. This phenomenon has now been quantitated and the distribution of mating-type loci in these "natural" amni-mating types determined.

Diploidy↗
PubMed1976

Regulation of mating and meiosis in yeast by the mating-type region.

A supposed sporulation-deficient mutation of Saccharomyces cerevisiae is found to affect mating in haploids and in diploids, and to be inseparable from the mating-type locus by recombination. The mutation is regarded as a defective a allele and is designated a*. This is confirmed by its dominance relations in diploids, triploids, and tetraploids. Tetrad analysis of tetraploids and of their sporulating diploid progeny suggests the existence of an additional locus, RME, which regulates sporulation in yeast strains that can mate. Thus the recessive homozygous constitution rme/rm- enables the diploids a*/alpha, a/a*, and alpha/alpha to go through meiosis. Haploids carrying rme show apparent premeiotic DNA replication in sporulation conditions. This new regulatory locus is linked to the centromere of the mating-type chromosome, and its two alleles, rme and RME, are found among standard laboratory strains.

Alleles↗
PubMed1979

Chemical carcinogenesis in nude mice: comparison between nude mice from homozygous matings and heterozygous matings and effect of age and carcinogen dose.

The incidence and latency periods for local tumor development after sc injection of 3-methylcholanthrene (MCA) into 30-day-old nude mice (nu/nu partially inbred on the CBA/H background) derived from homozygous matings (nu/nu times nu/nu) or heterozygous matings (nu/+ times nu/+) were comparable and did not differ with the immunologically normal controls, even when the carcinogen dosages ranged from 0.01 to 0.10 mg. Similarly, no differences in tumor incidence or latency periods between nude mice from homozygous or heterozygous matings as well as their immunologically normal controls were observed when weight-adjusted doses of MCA equivalent to 0.02 to 0.10 mg in the 30-day-old mice were administered at 120, 210, or 360 days of age. Tumor incidence was lower in nude mice and normal mice when MCA was administered at 210 and 360 days of age, especially in mice given the lower dose of MCA. The lower dosages of MCA (0.01-0.05 mg) had no detectable immunodepressive effects in normal mice. Thus the "normal" tumor incidence in nude mice after MCA administration could not be attributed to: 1) the effect of humoral thymus gland function (in the nude mice derived from heterozygous matings), 2) the immunodepressive effects of the carcinogen (the lower MCA dosages are not immunodepressive), or 3) the age of the mice at administration. These results argue against the thymus dependency of immunologic surveillance.

Age Factors↗
PubMed1975

Mating reaction in Saccharomyces cerevisiae. VIII. Mating-type-specific substances responsible for sexual cell agglutination.

The agglutination factors of a and alpha mating types of Saccharomyces cerevisiae were solubilized from isolated cell-wall fractions by treatment with snail enzyme (Glusulase) and shown to be adsorbed specifically by cells of the opposite mating type, resulting in the loss of agglutinability of these cells. The agglutination factors of a and alpha types adsorbed by cells of the opposite mating type at pH 5.5 were eluted at pH 9.0. These factors were further purified on Sepharose 4B. From the elution pattern on Sepharose 4B, the molecular weights of the solubilized agglutination factors are estimated to be about one million. Thus purified agglutination factors contained carbohydrate and protein and were considerably resistant to heat treatment. Neutral protease of Bacillus subtilis inactivated both a and alpha type agglutination factors. Trypsin inactivated the alpha type agglutination factor only.

Agglutination↗
PubMed1976

Mating reaction in Saccharomyces cerevisiae. X. Agglutinability-inactivating factor: a factor which destroys sexual agglutinability of a mating-type cells.

From cells of Saccharomyces cerevisiae a factor has been extracted that destroys the agglutinability of a mating-type cells specifically. It was found in the cell extracts of diploid and tetraploid strains as well as haploid strains of a and alpha mating types. It is heat-labile and the molecular weight is about 50,000. It is adsorbed by neither a cells nor alpha cells. Its biological activity is dependent on the incubation temperature and the pH, and is completely inhibited by phenylmethylsulfonyl fluoride, a potent inhibitor of the serine proteases. All the results described in this paper indicate that this factor is a proteolytic enzyme.

Adsorption↗
PubMed1977

a-Factor from Saccharomyces cerevisiae: partial characterization of a mating hormone produced by cells of mating type a.

Conjugation between haploid cells of Saccharomyces cerevisiae is mediated through the action of diffusible mating hormones, two of which have been designated as a-factor and alpha-factor. Partially purified fractions exhibiting a-factor activity have been obtained from culture filtrates of a cells by ultrafiltration, ion-exchange chromatography, and gel filtration. The a-factor preparations specifically caused both G1 arrest and morphological alterations in cells of alpha-mating type, whereas a cells, a/alpha diploids, and nonmating alpha mutants were not affected. The a-factor activity was found in the culture filtrates of all a strains tested, but not in filtrates of alpha or a/alpha cell cultures. The hormone is sensitive to various proteases, showing that it is associated with a peptide or protein. Gel filtration studies suggest an apparent molecular weight greater than 600,000; however, this result may be due to aggregation with carbohydrate present in the preparations. Although the biological activities of a-factor are analogous to those described previously for alpha-factor, the chemical properties of these two hormones appear to be quite different.

Cell Division↗
PubMed1976

Two-sided assortative mating for a single locus.

Most models previously considered for assortative mating were such that no change in gene frequencies occurred, or that one-sided assortative mating was occurring. Two-sided assortative mating is more realistic for human populations, and in this paper a model of two-sided assortative mating is analysed for two autosomal alleles with dominance, an important case for human genetics. The concept of a relative probability of matin between two phenotypes is used, and this variable can take into account factors such as different propensities for assortment in the various phenotypes and so forth. It is shown that the gene frequency may vary from generation to generation and conditions for the establishment of a stable polymorphism are given. For instance, Stanton (1947) has considered a special case of two-sided assortative mating with two autosomal alleles and a constant correlation between mates, where the value expressed by the heterozygote is numerically exactly half-way between the values exhibited by the two homozygotes. Also he has considered a special form of assortative mating, where the probability of occurrence of matings between the same homozygotes has been increased in each generation by the same constant factor as the probability of occurrence of matings between different homozygotes has been decreased. The probability of occurrence of matings involving heterozygotes remains the same as if mating were random. For this particular model the frequency of the genotypes in those who mate in generation t is the same as for the general population in generation t, but the genotypic frequencies change from generation to generation, reaching an equilibrium value. Stark (1976) has also considered a similar model to Stanton's (1947), the major difference occurring in the construction of the mating frequencies, which in this case occurs according to the canonical decomposition of the 2-way table of mating frequencies. Stark shows the correspondence between the results for this model and those given by Malécot (1939, 1948). The results for all these models depend on the particular values assigned to the genotypes. Also these models could be extended as outlined in this article for the case of two autosomal alleles with dominance.

Alleles↗