(n.) A small membranous bladder or tube in which are inclosed the seedlike reproductive particles or sporules of lichens and certain fungi.
Example Sentences:
(1) Fungi of the class Pyrenomycetes (Ascomycotina) form a morphological series ranging from those that shoot ascospores (sexual spores) forcibly from the ascus (spore sac) to fungi that ooze ascospores or have no obvious mechanism for ascospore release.
(2) Our results suggest that once the cells are fully derepressed no mitochondrial genetic information has to be expressed during meiosis and ascus formation.
(3) Although growth of two yeast strains characterized by consistent production of two diploid spores per ascus was inhibited in complex presporulation media containing amitrole, a fraction of the cells produced were able to form asci with more than two spores after transfer to acetate sporulation medium.
(4) Due to the characteristic shape of the ascus and ascospores, T. burgeffiana is to be considered a synonym of M. pulcherrima.
(5) Although the rna mutants do not regulate ribosome synthesis during sporulation, all of these diploid strains fail to complete sporulation at 34 degrees C. The cells are arrested after the second meiotic nuclear division but before ascus formation.
(6) strains develop normally to the stage of ascus formation.
(7) The selected hybrids, which carried the greater part of the parental genetic markers and produced asci containing 2,3 and 4 spores per ascus, were placed on sporulation medium.
(8) 2 x n X2 tests showed that frequencies of individual ascus classes from different perithecia were generally homogeneous, as were second division segregation frequencies.
(9) The proportion of spindle overlap and recombinational asci within the group did not change as shown by ascus dissection.
(10) It was demonstrated that the production of less than four spores per ascus in this yeast is not the result of a lack of meiotic products but of the nonutilization of nuclei from meiosis.
(11) The forespores then elongate, close off, and become separated from the ascus cytoplasm by membranes.
(12) The mechanical force responsible apparently originates from the formation of an ectoplasmic mucilage capable of exerting pressure over all of the ascus contents; when the apex of the peduncle ruptures, the ascospores are violently released.
(13) When partially repressed cells were treated with EthBr, no ascus formation was observed after transfer to sporulation medium.
(14) In fungi that produce an ascus containing four spores, a gene conversion event is manifested as 3:1 or 1:3 (or more rarely 4:0 or 0:4) segregations, in contrast to the normal mendelian 2:2 segregation.
(15) The increase in spore numbers per ascus is attributed either to the induction by amitrole in growth medium of cells with more than one nucleus or to the restoration of normal meioses in the multispored asci.
(16) On the basis of mode of ascus formation and ascospore morphology it is included in the genus Metschnikowia Kamienski as a new species, M. lunata.
(17) Ascus formation occurs after isogamous copulation between sexual protuberances which develop at the ends of arthrospores or between two cells, adjacent mycelial cells, or arthrospores.
(18) Ascus formation in Debaryomyces hansenii includes fusion of two cells, usually mother and daughter while still attached to each other, through short protuberances developed from the cross wall between them.
(19) Metschnikowia australis can be differentiated from other Metschnikowia species and varieties by its inability to form chlamydospores, the formation of two needle-shaped ascospores per ascus, lack of glucose fermentation, and lack of assimilation of both methyl-alpha-D-glucoside and glucono-delta-lactone.
(20) Amitrole treatment causes multispored ascus production by cells of a yeast strain whose asci normally contain two diploid spores.
Meiosis
Definition:
(n.) Diminution; a species of hyperbole, representing a thing as being less than it really is.
Example Sentences:
(1) To this end, a meiosis-defective mating-type mutation was used as a marker for the plus segment, by taking advantage of its suppressibility by a nonsense suppressor.
(2) When multiple probes were informative, the meiotic exchange points for each meiosis were located in individual families.
(3) This observation suggests that testosterone acts to inhibit meiosis at a site beyond the function of the puromycin-sensitive proteins or that testosterone causes a reduction in the turnover rate of these proteins.
(4) Commitment to meiosis occurs during the prezygotene interval at about the time when S-phase replication is completed.
(5) Meiosis is too complex to have arisen at once full blown and a stepwise scheme is proposed for its evolution, where each step is believed to have provided an immediate selective advantage: (1) The first step in this tentative sequence is the development of a haploidization process by means of a rapid series of mitotic non-disjunctions, turned on under conditions where haploidy is favored.
(6) Recently, cDNA clones encoding several bovine CKI isoforms have been sequenced that show high sequence identity to the HRR25 gene product of the budding yeast Saccharomyces cerevisiae; HRR25 is required for normal cellular growth, nuclear segregation, DNA repair, and meiosis.
(7) They proceed through meiosis normally, as judged by the occurrence of meiotic recombination, the production of haploid nuclei, and the formation of multinucleate cells visible after Giemsa staining.
(8) In continuation of the research on male human meiosis within the study of pachytene bivalents, results from the analysis of 125 cells are presented.
(9) The absence of these mRNAs in mitosis and their disappearance at 4 hr and later in meiosis suggest that the rec7 and rec8 gene products may be involved primarily in the early steps of meiotic recombination in S. pombe.
(10) This trisomy arose through aberrant segregation of translocation chromosome during meiosis in the patient's mother, who is a balanced heterozygote for a complex translocation involving chromosomes 9, 21 and 22.
(11) Chemicals were injected into mice at the MI (meiosis I) stage or 3 hours before the MI stage in order to examine their toxicity.
(12) In the immunogold staining assay a post-fixation and nuclear staining procedure was developed which allowed identification of isolated germ cells, revealing clearly, for all seven MAbs, that the determinants were expressed on germ cells but not on somatic cells and, for WCS 7, 11 and 12 only, that the determinants first appeared on small spermatogonia prior to meiosis.
(13) A 'small' CG-free area of the cortex, with prominent cytoplasmic protrusions, appeared twice during the progression of meiosis.
(14) An attractive explanation for these results is that long tandem arrays of simple repeated sequences are generated at high frequency throughout the genome and that they are retained for a longer time on the Y chromosome due to the absence of homologous pairing at meiosis.
(15) Expression of one of the three genes was found to be limited to a single cell type during the 5-6 day period from late meiosis to immature pollen formation.
(16) Analysis of RNA from different developmental stages and from enriched populations of spermatogenic cells revealed that this gene is expressed during the prophase stage of meiosis.
(17) In fission yeast the ability to undergo meiosis and sporulation is conferred by the matP+ and matM+ genes of the mating-type locus.
(18) The binding of in vivo labeled RNA to the corresponding DNAs increased 3- to 12-fold at the time of meiosis I, in parallel with the accumulation of the SPR transcripts.
(19) It was concluded that meiosis and spore formation in Saccharomycopsis lipolytica seem to represent parallel and coordinated processes which generally resemble those recorded for Saccharomyces cerevisiae and Hansenula species.
(20) Neither meiosis nor mutagenesis increased the revertant frequency, nor did incubation at elevated temperatures lower it.