Use of Neurospora Spore killer strains to obtain centromere linkage data without dissecting asci

1986 ◽  
Vol 28 (6) ◽  
pp. 971-981 ◽  
Author(s):  
David D. Perkins ◽  
Namboori B. Raju ◽  
Virginia C. Pollard ◽  
Joseph L. Campbell ◽  
Adam M. Richman
Keyword(s):  
Meiotic Division ◽  
Nuclear Division ◽  
Linkage Data ◽  
Crossing Over ◽  
Tetrad Analysis ◽  
Marker Alleles ◽  
Spore Killer ◽  
Killer Gene

Use of a centromere-linked Spore killer gene Sk reduces manyfold the labor involved in obtaining tetrad data that would otherwise require ordered dissection of intact linear eight-spored asci. Heterozygous crosses are made for Spore killer (SkK × SkS) and for markers to be tested. In such crosses only SkK ascospores survive. The four viable (SkK) and four aborted (SkS) ascospores of each ascus are ejected from the perithecium as a physically disordered group. The four surviving SkK ascospores of individual asci are germinated and scored. SkK segregates from SkS at the first meiotic division. If both marker alleles are represented in the surviving products, they must therefore have segregated from one another at the second division. Four-spore (Fsp) genes have been used to eliminate one postmeiotic nuclear division, so that only two ascospores per ascus need to be scored. The Spore killer method has been useful for mapping closely linked genes in centromere regions, for identifying genes that are far out on chromosome arms, for obtaining information on meiotic crossing-over, and for comparing linkages in different species.Key words: tetrad analysis, centromere mapping, Spore killer, Neurospora.

Diploid female gametophyte formation in 24-chromosome potatoes: genetic evidence for the prevalence of the second meiotic division restitution mode

1986 ◽  
Vol 28 (1) ◽  
pp. 101-108 ◽  
Author(s):  
David M. Stelly ◽  
Stanley J. Peloquin
Keyword(s):  
Meiotic Division ◽  
Female Gametophyte ◽  
Alternative Explanation ◽  
Crossing Over ◽  
Mechanism Of Formation ◽  
Tetrad Analysis ◽  
Origin And Evolution ◽  
Diploid Female ◽  
Solanum Spp ◽  
Map Distance

Half-tetrad genetic analysis of 1431 plants in 26 4x potato (Solanum spp.) families from 2x × 4x crosses revealed that at least 20 of the 26 female parents form 2n female gametophytes that are predominantly or exclusively of the second meiotic division restitution (SDR) type. SDR 2n gametophytes genetically equate to gametophytes that would result from restitution of the second meiotic division. Previous estimates obtained by half-tetrad analysis with 2n pollen placed the yellow-tuber flesh marker, Y, at 13 map units from its centromere. Overall ratios observed herein were slightly discordant with predictions based on that estimate, indicating that the map distance (p) may be slightly greater, around 18.5 map units. An alternative explanation is that most of the tested parents produce a mixture of 2n female gametophytes, composed of mostly SDR but also a smaller proportion of FDR or FDR-NCO 2n female gametophytes. Genetically, FDR and FDR-NCO 2n gametophytes equate to those resulting from meiotic first division restitution, with, or with no crossing-over, respectively. Because the data do not discriminate between these hybpotheses, the segregation data were tested according to both estimates of p. Results with six additional clones were inconclusive regarding the mode of 2n gametophyte formation. The results illustrate limitations of half-tetrad analyses for determining the exact composition of 2n gametophyte populations, where these might result from more than one mechanism of formation. The finding that SDR 2n female gametophytes were most prevalent nevertheless supports the hypothesis that they have contributed significantly to the origin and evolution of the tetraploid cultivated potato, and that SDR × FDR or SDR × FDR-NCO crosses (2x × 2x) may be a meritorious approach for potato improvement.Key words: meiosis, Solanum, evolution, breeding.

scholarly journals ISOLATION OF SPO12–1 AND SPO13–1 FROM A NATURAL VARIANT OF YEAST THAT UNDERGOES A SINGLE MEIOTIC DIVISION

Genetics ◽  
1980 ◽  
Vol 96 (3) ◽  
pp. 567-588 ◽  
Author(s):  
Sue Klapholz ◽  
Rochelle Easton Esposito
Keyword(s):  
Genetic Analysis ◽  
Meiotic Division ◽  
Parental Strain ◽  
Nuclear Division ◽  
Nuclear Genes ◽  
Vegetative Cells ◽  
Total Level ◽  
Natural Variant ◽  
Chromosome Viii

ABSTRACT ATCC4117 is a strain of S. cerevisiae that undergoes a single nuclear division during sporulation to produce asci containing two diploid ascospores (Grewal and Miller 1972). All clones derived from these spores are sporulation-capable and, like the parental strain, form two-spored asci. In this paper, we describe the genetic analysis of ATCC4117. In tetraploid hybrids of vegetative cells of the ATCC4117 diploid and a/a or α/α diploids, the production of two-spored asci is recessive. From these tetraploids, we have isolated two recessive alleles, designated spo12–1 and spo13–1, each of which alone results in the production of asci with two diploid or near-diploid spores. These alleles are unlinked and segregate as single nuclear genes. spo12–1 is approximately 22 cM from its centromere; spo13–1 has been localized to within 1 cM of arg4 on chromosome VIII. This analysis also revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation.

scholarly journals Gene conversion: observations on the DNA hybrid models

1970 ◽  
Vol 15 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Andrzej Paszewski
Keyword(s):  
Experimental Data ◽  
Gene Conversion ◽  
Hybrid Models ◽  
Crossing Over ◽  
Meiotic Segregation ◽  
Tetrad Analysis ◽  
Dna Models ◽  
Complex Picture ◽  
New Hypothesis ◽  
Hybrid Dna

SUMMARYSome features of gene conversion in fungi and their bearing on the hybrid DNA models are discussed. Available experimental data from tetrad analysis seem to give a more complex picture of polarity in intra-genic recombination and of the relations between conversion and post-meiotic segregation, and between conversion and crossing-over, than predicted by the models.A new hypothesis of the mechanism of gene conversion with special attention given to the aspect of asymmetry in this phenomenon is proposed as an alternative to the mechanism suggested by the DNA hybrid models.

scholarly journals Linkage relationships of markers on chromosome 17 of the house mouse

1975 ◽  
Vol 26 (2) ◽  
pp. 203-211 ◽  
Author(s):  
Graig Hammerberg ◽  
Jan Klein
Keyword(s):  
House Mouse ◽  
Chromosomal Region ◽  
Recombination Frequency ◽  
Genetic Distances ◽  
Chromosome 17 ◽  
Linkage Data ◽  
Crossing Over ◽  
The Right ◽  
Linkage Relationships ◽  
Important Marker

SUMMARYLinkage data for the following markers on chromosome 17 of the house mouse were obtained: centromere (marked by translocation R67), Brachyury (T), tufted (tf), H-2, and thin fur (thf). The markers were found to be arranged in that order in the genetic map and the combined genetic distances between individual markers were found to be as follows: Rb7…T, 4·5 cM; T…tf, 5·8 cM; tf…H-2, 5·0 cM; H-2…thf, 15·1 cM. The localization of the thf locus on the non-centromeric side of the H-2 complex provides an important marker for this arm of chromosome 17. The map distances in the centromeric portion of chromosome 17 changed drastically in the presence of various t factors. These factors strongly reduce the recombination frequency in the T…tf and tf…H-2 intervals and this crossing-over suppression is most likely responsible for the linkage disequilibrium between t and H-2 reported earlier. Recombinants involving a t chromosome but occurring to the right of the H-2 complex do not change the properties of t factors suggesting that all determinants responsible for the t phenotype are located in the chromosomal region between T and tf (H-2).

High resolution map around the vrs1 locus controlling two- and six-rowed spike in barley, Hordeum vulgare

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 248-253 ◽  
Author(s):  
Takao Komatsuda ◽  
Wenbin Li ◽  
Fumio Takaiwa ◽  
Seibi Oka
Keyword(s):  
Hordeum Vulgare ◽  
Mapping Population ◽  
Recombination Frequency ◽  
Linkage Study ◽  
Linkage Data ◽  
Published Data ◽  
Crossing Over ◽  
Lateral Spikelet ◽  
Significant Difference ◽  
High Resolution Map

The vrs1 (formerly v) locus in the long arm of chromosome 2H controls lateral spikelet development in barley. The vrs1 locus was mapped by backcross-derived lines that consisted of 373 BC7F1 plants and 278 BC6F2 plants. The linkage study indicated that MWG801, CMNA-38/700, cMWG699, vrs1 and MWG865 exist in the order listed, with map distances of 3.1, 0.4, 0.1, and 0.9 centimorgans (cM), respectively. Recombination in female and male meiocytes showed no significant difference within this region. In a neighboring region between MWG865 and MWG503, the recombination frequency was higher in female than male meiocytes in one mapping population. The combined linkage data obtained from this study were compared with published data, and genotype-specific suppression of crossing-over was not evident in the vrs1 region.Key words: vrs1 locus (two- vs. six-rowed), molecular marker, recombination, backcross, Hordeum vulgare.

Genetic implications of current models of somatic nuclear division in fungi

1972 ◽  
Vol 50 (6) ◽  
pp. 1337-1347 ◽  
Author(s):  
Alan W. Day
Keyword(s):  
Nuclear Division ◽  
Crossing Over ◽  
Somatic Segregation ◽  
The Third ◽  
Chromosome Distribution ◽  
Experimental Approaches ◽  
Distribution Studies

The unusual two-track type of division which is widespread in most fungi other than Phycomycetes is described. Three models which attempt to account for this type of division are discussed in relation to (i) genetical observations on somatic segregation and (ii) chromosome distribution studies which predict that chromosomes of similar genetic 'age' move as a set. The feasibility of two of the models which postulate that the chromosomes are linked in chains is discussed in the light of our knowledge of mitotic crossing-over and haploidization. The third model (Robinow and Caten 1969) is more orthodox and differs from classical mitosis only in the presence of a narrow intranuclear spindle around which the chromosomes attach randomly and disjoin asynchronously. Future experimental approaches to distinguish between these models and to define the mechanism of division more completely are suggested.

scholarly journals The Ade6-M26 Mutation of Schizosaccharomyces Pombe Increases the Frequency of Crossing over.

Genetics ◽  
1988 ◽  
Vol 119 (3) ◽  
pp. 507-515
Author(s):  
P Schuchert ◽  
J Kohli
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Marker Gene ◽  
Crossing Over ◽  
Crossover Frequency ◽  
Tetrad Analysis ◽  
Ectopic Recombination ◽  
Homologous Sequences ◽  
New Information ◽  
Conversion Frequency

Abstract The ade6-M26 mutation of Schizosaccharomyces pombe increases conversion frequency in comparison with the nearby mutation ade6-M375. In order to investigate the effect of ade6-M26 on crossover frequency, heteroallelic ade6 duplications were constructed by integration of plasmids carrying the marker gene ura4. One ade6 gene carries either of the mutations M26 or M375 while the other ade6 copy carries the L469 mutation in both duplications. The duplication with ade6-M26 yields Ade(+) recombinants at significantly higher frequencies in meiosis, but not in mitosis. Tetrad analysis and physical characterization of spore clones from recombination tetrads demonstrate that conversions, unequal crossovers and intrachromatid exchanges occur at higher frequencies but with unaltered proportions among them. The conversion events show a pronounced bias when M26 is involved: they take place preferentially at the M26 allele. Thus the ade6-M26 mutation not only enhances conversion frequency as demonstrated before, but also crossover frequency. It displays the properties expected for a preferred site of initiation of general meiotic recombination. The duplications also yielded new information on ectopic recombination in S. pombe: ectopic crossovers occur in the duplications at much higher frequency than among naturally dispersed homologous sequences.

scholarly journals Memoirs: The Male Meiotic Phase in Two Genera of Marsupials (Macropus and Petauroides)

1923 ◽  
Vol s2-67 (266) ◽  
pp. 183-202
Author(s):  
W. E. AGAR
Keyword(s):  
Chromosome Number ◽  
Sex Chromosomes ◽  
Meiotic Division ◽  
Ovarian Follicle ◽  
The Other ◽  
Pachytene Stage ◽  
Follicle Cells ◽  
Crossing Over ◽  
Early Pachytene ◽  
Spermatogonial Metaphase

Macropus ualabatus has twelve chromosomes, namely 10 + XY in the male and 10 + XX in the female. In Petauroides the number is almost certainly twenty-two, the male being of the formula 20 + XY. No female counts were obtained for this animal. In the male Macropus Xis generally attached to one of the autosomes in spermatogonial mitoses. Y, which is exceedingly minute, is free. During the pachytene stage, while the autosomes are still elongated, X and Y condense into a bivalent. In the first meiotic division this bivalent is attached to an autosome. As a result of the first meiotic division the usual two classes of secondary spermatocytes are formed one with X and the other with Y. In the second meiotic division, those with X show only five separate chromosomes, showing that X, as usual, is fused with an autosome. The other class of second divisions shows five autosomes and the minute Y. In the female Macropus the sex chromosomes were never found free from the autosomes in the ovarian follicle cells, which therefore show only ten separate chromosomes. In Petauroides the sex chromosomes cannot be distinguished with certainty from the autosomes. An unequal pair of small chromosomes usually situated in the centre of the spermatogonial metaphase plates probably, however, are X and Y. Early pachytene nuclei show two compact bodies which unite into one, presumably the sex bivalent. The second reduction of the chromosome number to onequarter of the diploid total in the second meiotic division, which has been described for several species of birds and mammals, does not take place either in Macropus or Petauroides. Chromomeres are very prominent in Petauroides in the zygotene and diplotene stages. Probably in Macropus, and more convincingly in Petauroides, the cytological conditions to permit of ‘crossing over’ are present in the male. The plasmosome which appears in the pachytene stage is probably formed from the plastin or linin basis of the contracting sex chromosomes.

scholarly journals Sexual dimorphism in mouse gametogenesis

1960 ◽  
Vol 1 (3) ◽  
pp. 477-486 ◽  
Author(s):  
B. M. Slizynski
Keyword(s):  
Sexual Dimorphism ◽  
Meiotic Division ◽  
Chiasma Formation ◽  
Meiotic Metaphase ◽  
Pachytene Stage ◽  
Crossing Over ◽  
Adult Males ◽  
Present Technique ◽  
Metaphase Stage ◽  
Gametic Selection

Diplotene and diakinesis chiasma frequency in oöcytes of the mouse cannot be studied successfully with the present technique. Metaphase chiasmata have been examined in thirty-nine oöcytes. It is deduced that the total diplotene map length in females is about 2300 cM. compared with 1950 cM. in males. There is sexual dimorphism in the frequency of chiasmata, which is paralleled by similar dimorphism in frequencies of crossing-over, measured genetically.The two sexes differ in the duration of various stages of meiosis. In adult males the pachytene stage, lasting for about 7 days, is directly followed by diplotene and diakinesis, after which the metaphase stage sets in. The sex bivalent in males develops visible chiasmata much earlier than do the autosomes and it precedes them in anaphase separation. Quick terminalization of chiasmata in it leads in a fair proportion of cases to precocious separation and in less than 1% of cases to cytologically detectable non-disjunction of sex chromosomes.In females the pachytene stage appears in oöcytes of the embryo and is followed by the dictyotene stage, which last still ovulation, i.e. between 35–40 days and several months. Since in the oöcyte chiasmata are formed and move during the dictyotene stage, it follows that stainable materials of the chromosomes are not necessary for the formation and movement of chiasmata and are concomitant with pairing and anaphase separation. It follows also that the time for chiasma formation and movement is in females at least five to six times longer than in males. In old oöcytes in which time is available for maximum terminalization of chiasmata, non-disjunction may appear with detectable frequency. This mechanism may also operate in cases of Mongolism in man, where non-disjunction of an autosome has been recently cytologically established and higher frequency of incidence of the condition for old mothers has been known for some time.It is possible that the differences in duration of various stages of gametogenesis are connected with the period at which gametic selection is operating: in spermatogenesis after the second meiotic division, in oögenesis prior to first meiotic metaphase.

scholarly journals MAPPING AND GENE CONVERSION STUDIES WITH THE STRUCTURAL GENE FOR ISO-1-CYTOCHROME C IN YEAST

Genetics ◽  
1975 ◽  
Vol 81 (4) ◽  
pp. 615-629
Author(s):  
Christopher W Lawrence ◽  
Fred Sherman ◽  
Mary Jackson ◽  
Richard A Gilmore
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
The Other ◽  
Crossing Over ◽  
Wild Type ◽  
Chromosome X ◽  
Tetrad Analysis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Distal Marker ◽  
The Right

ABSTRACT We have investigated the order of the four genes cyc1, rad7, SUP4, and cdc8 which form a tightly linked cluster on the right arm of chromosome X in the yeast Saccharomyces cerevisiae. Crossing over and coconversion data from tetrad analysis established the gene order to be centromere–cyc1–rad7–SUP4. Also cdc8 appeared to be distal to SUP4 on the basis of crossovers that were associated with conversion of SUP4. The frequencies of recombination and the occurrence of coconversions suggest that these four genes are contiguous or at least nearly so. Gene-conversion frequencies for several cyc1 alleles were studied, including cyc1–1, a deletion of the whole gene that extends into the rad7 locus. The cyc1–1 deletion was found to be capable of conversion, though at a frequency some fivefold less than the other alleles studied, and both 3:1 and 1:3 events were detected. In general 1:3 and 3:1 conversion events were equally frequent at all loci studied, and approximately 50% of conversions were accompanied by reciprocal recombination for flanking markers. The orientation of the cyc1 gene could not be clearly deduced from the behavior of the distal marker SUP4 in wild-type recombinants that arose from diploids heteroallelic for cyc1 mutations.

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