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 Memoirs: Marsupial Spermatogenesis

1923 ◽  
Vol s2-67 (266) ◽  
pp. 203-218
Author(s):  
A. W. GREENWOOD
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Meiotic Division ◽  
Sex Chromosome ◽  
The Other ◽  
Pachytene Stage ◽  
Late Pachytene ◽  
Early Pachytene ◽  
Y Chromosomes ◽  
And Function

In the three animals studied the total number of chromosomes in the male is as follows : Phascolarctus 16 (14 autosomes + XY). Sarcophilus 14 (12 autosomes + XY). Dasyurus 14 (12 autosomes + XY). In the female the number of chromosomes is as follows : Phascolarctus 16 (14 autosomes + XX). Sarcophilus 14 (12 autosomes + XX). In all animals dealt with in this paper the Y-chromosome is very minute in size compared with the other chromosomes; also the X-chromosome is much smaller than any of the autosomes. Chromomeres are conspicuous during syndesis, early pachytene, and early diplotene stages. The early pachytene stage is followed by a late pachytene stage in which the threads become diffuse and lose their capacity for taking up the stain. Except in the early meiotic prophase the sex chromosome remains compact and deeply stained and does not thread out like the autosomes. In all the above animals the first meiotic division is reductional, separating the X- and the Y-chromosomes, and the second division is equational, in each cell the sex chromosome dividing. The spermatozoa are therefore of two kinds, one containing an X-chromosome and the other containing a Y-chromosome. No further reduction in the number of chromosomes takes place during the second meiotic division. The Y-chromosome could not be identified during the meiotic phase until the metaphase of the first meiotic division. At this stage in Phascolarctus the sex chromosomes are separate and do not form a bivalent. The archoplasm seems to exert some influence on the chromatin threads at synizesis and during the early pachytene stage. In the former case the contraction takes place to that side of the nucleus at which the archoplasmic mass is situated; in the latter the chromosomes are in the form of thick loops with the ends of the chromosomes pointing towards the archoplasmic mass. In Phascolarctus the Sertoli cells are very large and possess peculiar rod-like bodies, the origin and function of which was not arrived at. The result of experiments seem to show that the rods are not affected by the action of digestive fluids.

The chromosomes of Metachirus nudicaudatus (Marsupialia : Didelphidae)

1973 ◽  
Vol 21 (3) ◽  
pp. 369 ◽  
Author(s):  
E Yunis ◽  
J Cayon ◽  
E Ramirez
Keyword(s):  
Chromosome Number ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Evolutionary History ◽  
Meiotic Chromosome ◽  
Staining Technique ◽  
Pachytene Stage ◽  
Apparent Lack ◽  
Heterochromatin Staining ◽  
Metachirus Nudicaudatus

A karyologic study of M. nudicaudatus, carried out on three females and five males, shows a chromosome number of 14, with apparent lack of dimorphism in the sex chromosomes. Nevertheless, the heterochromatin staining technique reveals the Y chromosome to be fully heteropycnotic. The meiotic chromosome has a sex vesicle at the pachytene stage. The similarity of this karyotype with those of Caluromys derbianus and Dromiciops australis is striking, especially considering that the genera belong to two subfamilies separated early in their evolutionary history. Our results support the opinion of Hayman and Martin that the original chromosome number in Marsupialia was 14.

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.

Three-to-one segregation from reciprocal translocation quadrivalents in Neurospora and its bearing on the interpretation of spore-abortion patterns in unordered asci

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 661-672 ◽  
Author(s):  
David D. Perkins ◽  
Namboori B. Raju
Keyword(s):  
Frequency Characteristic ◽  
Meiotic Division ◽  
Reciprocal Translocation ◽  
Visual Inspection ◽  
Chromosome Rearrangement ◽  
The Other ◽  
Sequence Information ◽  
Crossing Over ◽  
Distal Half ◽  
Basal Half

In Neurospora, viable ascospores become black (B) when mature, whereas ascospores that are deficient for a chromosome segment are inviable and usually fail to blacken. The presence of a chromosome rearrangement can be recognized and the type of rearrangement can usually be inferred by visual inspection of asci. When a cross is heterozygous for a reciprocal translocation, asci with eight black ascospores (8B:0W) and asci with eight abortive unpigmented ("white" (W)) ascospores (0B:8W) are theoretically produced in equal numbers if homologous centromeres are equally likely to segregate from the quadrivalent in alternate or adjacent modes. In addition, 4B:4W asci are produced with a frequency characteristic of each reciprocal translocation. Information on ascospore-abortion patterns in Neurospora crassa has come predominantly from unordered ascospore octads ejected from the perithecium. Unordered asci of the 4B:4W type were initially presumed to originate by interstitial crossing over in a centromere-breakpoint interval and their frequency was used as a predictor of centromere locations. However, 4B:4W asci can result not only from interstitial crossing over but also from nondisjunction of centromeres at the first meiotic division, which leads to 3:1 segregation. Ordered linear 4B:4W asci retain the sequence information necessary for distinguishing one mode of origin from the other but unordered asci do not. Crossing over results in one abortive duplication–deficiency ascospore pair in each opposite half of a linear ascus, while 3:1 segregation places both abortive ascospore pairs together, either in the distal half or the basal half of the ascus. In the present study, perithecia were opened and intact linear asci were examined in crosses heterozygous for a varied sample of translocations. Three-to-one segregation rather than interstitial crossing over is apparently the main cause of 4B:4W asci when breakpoints are near centromeres, whereas crossing over is responsible for most or all 4B:4W asci when breakpoints are far-distal. Three-to-one segregation does not impair the usefulness of ejected unordered asci for detecting chromosome rearrangements. Ejected octads are superior to ordered linear asci for distinguishing one type of rearrangement from another, because ascus ejection from the perithecium does not occur until viable ascospores are fully pigmented, enabling true 0B:8W asci to be distinguished from those with eight immature ascospores.Key words: ascospore abortion, ascus analysis, Neurospora, nondisjunction, reciprocal translocation, three-to-one segregation.

scholarly journals The Reduction of Chromosome Number in Meiosis Is Determined by Properties Built into the Chromosomes

2000 ◽  
Vol 150 (6) ◽  
pp. 1223-1232 ◽  
Author(s):  
Leocadia V. Paliulis ◽  
R. Bruce Nicklas
Keyword(s):  
Chromosome Number ◽  
Meiotic Division ◽  
Spindle Pole ◽  
The Other ◽  
Whole Cell ◽  
Sister Chromatids ◽  
Meiosis I

In meiosis I, two chromatids move to each spindle pole. Then, in meiosis II, the two are distributed, one to each future gamete. This requires that meiosis I chromosomes attach to the spindle differently than meiosis II chromosomes and that they regulate chromosome cohesion differently. We investigated whether the information that dictates the division type of the chromosome comes from the whole cell, the spindle, or the chromosome itself. Also, we determined when chromosomes can switch from meiosis I behavior to meiosis II behavior. We used a micromanipulation needle to fuse grasshopper spermatocytes in meiosis I to spermatocytes in meiosis II, and to move chromosomes from one spindle to the other. Chromosomes placed on spindles of a different meiotic division always behaved as they would have on their native spindle; e.g., a meiosis I chromosome attached to a meiosis II spindle in its normal fashion and sister chromatids moved together to the same spindle pole. We also showed that meiosis I chromosomes become competent meiosis II chromosomes in anaphase of meiosis I, but not before. The patterns for attachment to the spindle and regulation of cohesion are built into the chromosome itself. These results suggest that regulation of chromosome cohesion may be linked to differences in the arrangement of kinetochores in the two meiotic divisions.

New cytogenetic data on Coreoidea (Hemiptera: Heteroptera) with special reference to Coreidae

Zootaxa ◽  
2012 ◽  
Vol 3313 (1) ◽  
pp. 53 ◽  
Author(s):  
HAILIN YANG ◽  
HU LI ◽  
XUN DAI ◽  
JIAN CHANG ◽  
WANZHI CAI
Keyword(s):  
Chromosome Number ◽  
Special Reference ◽  
Sex Chromosomes ◽  
Meiotic Division ◽  
Phylogenetic Relationships ◽  
Male Meiosis ◽  
Point Of View ◽  
Diploid Chromosome Number ◽  
Holokinetic Chromosomes ◽  
The Family

Some cytogenetic aspects of six Chinese species of Coreoidea were studied. The material included five species from the familyCoreidae: Hydarella orientalis (Distant), Homoeocerus bannaensis Hsiao, Cletus graminis Hsiao & Cheng, Paradasynus lon-girostris Hsiao, Acanthocoris scaber (Linnaeus), and one species from the family Stenocephalidae: Stenocephalus femoralisReuter. All species show holokinetic chromosomes, post-reductional meiotic division of XO sex chromosomes, a pre-reduc-tional type of meiosis for autosomes and m-chromosomes, intersticial chiasmata in most autosomes, and one chiasma per biva-lent in male meiosis. In the species studied, the diploid chromosome number ranged from 13 to 21. It was 13 in S. femoralis (10+ 2m + XO), 15 in Hy. orientalis (12 + 2m + XO), 17 in Ho. bannaensis (14 + 2m + XO) and C. graminis (14 + 2m + XO), 19in P. longirostris (16 + 2m + XO), and 21 in A. scaber (18 + 2m + XO). Hy. orientalis represents the first cytogenetically stud-ied species in subfamily Hydarinae. The phylogenetic relationships among Coreoidea are briefly discussed from a cytogenetic point of view.

scholarly journals Limitation of current probe design for oligo-cross-FISH, exemplified by chromosome evolution studies in duckweeds

Chromosoma ◽  
2021 ◽  
Vol 130 (1) ◽  
pp. 15-25
Author(s):  
Phuong T. N. Hoang ◽  
Jean-Marie Rouillard ◽  
Jiří Macas ◽  
Ivona Kubalová ◽  
Veit Schubert ◽  
...  
Keyword(s):  
Growth Rate ◽  
Chromosome Number ◽  
Chromosome Evolution ◽  
Sequence Similarity ◽  
Flowering Plants ◽  
The Other ◽  
Probe Design ◽  
Congeneric Species ◽  
Specific Design ◽  
Spirodela Polyrhiza

AbstractDuckweeds represent a small, free-floating aquatic family (Lemnaceae) of the monocot order Alismatales with the fastest growth rate among flowering plants. They comprise five genera (Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia) varying in genome size and chromosome number. Spirodela polyrhiza had the first sequenced duckweed genome. Cytogenetic maps are available for both species of the genus Spirodela (S. polyrhiza and S. intermedia). However, elucidation of chromosome homeology and evolutionary chromosome rearrangements by cross-FISH using Spirodela BAC probes to species of other duckweed genera has not been successful so far. We investigated the potential of chromosome-specific oligo-FISH probes to address these topics. We designed oligo-FISH probes specific for one S. intermedia and one S. polyrhiza chromosome (Fig. 1a). Our results show that these oligo-probes cross-hybridize with the homeologous regions of the other congeneric species, but are not suitable to uncover chromosomal homeology across duckweeds genera. This is most likely due to too low sequence similarity between the investigated genera and/or too low probe density on the target genomes. Finally, we suggest genus-specific design of oligo-probes to elucidate chromosome evolution across duckweed genera.

scholarly journals MITOTIC CROSSING OVER AND NONDISJUNCTION IN TRANSLOCATION HETEROZYGOTES OF ASPERGILLUS

Genetics ◽  
1976 ◽  
Vol 82 (4) ◽  
pp. 605-627
Author(s):  
Etta Käfer
Keyword(s):  
Selective Advantage ◽  
The Other ◽  
Translocation Chromosome ◽  
Crossing Over ◽  
Selective Marker ◽  
Reciprocal Translocations ◽  
Poor Growth ◽  
Different Types ◽  
Diploid Genotype ◽  
One Step

ABSTRACT To analyze mitotic recombination in translocation heterozygotes of A. nidulans two sets of well-marked diploids were constructed, homo- or heterozygous for the reciprocal translocations T1(IL;VIIR) or T2(IL;VIIIR) and heterozygous for selective markers on IL. It was found that from all translocation heterozygotes some of the expected mitotic crossover types could be selected. Such crossovers are monosomic for one translocated segment and trisomic for the other and recovery depends on the relative viabilities of these unbalanced types. The obtained segregants show characteristically reduced growth rates and conidiation dependent on sizes and types of mono- and trisomic segments, and all spontaneously produce normal diploid sectors. Such secondary diploid types either arose in one step of compensating crossing over in the other involved arm, or—more conspicuously—in two steps of nondisjunction via a trisomic intermediate.—In both of the analyzed translocations the segments translocated to IL were extremely long, while those translocated from IL were relatively short. The break in I for T1(I;VII) was located distal to the main selective marker in IL, while that of T2(I;VIII) had been mapped proximal but closely linked to it. Therefore, as expected, the selected primary crossover from the two diploids with T2(I;VIII) in coupling or in repulsion to the selective marker, showed the same chromosomal imbalance and poor growth. These could however be distinguished visually because they spontaneously produced different trisomic intermediates in the next step, in accordance with the different arrangement of the aneuploid segments. On the other hand, from diploids heterozygous for T1(I;VII) mitotic crossovers could only be selected when the selective markers were in coupling with the translocation; these crossovers were relatively well-growing and produced frequent secondary segregants of the expected trisomic, 2n+VII, type. For both translocations it was impossible to recover the reciprocal crossover types (which would be trisomic for the distal segments of I and monosomic for most of groups VII or VIII) presumably because these were too inviable to form conidia.—In addition to the selected segregants of expected types a variety of unexpected ones were isolated. The conditions of selection used favour visual detection of aneuploid types, even if these produce only a few conidial heads and are not at a selective advantage. For T2(I;VIII) these "non-selected" unbalanced segregants were mainly "reciprocal" crossovers of the same phenotype and imbalance as the selected ones. For T1(I;VII) two quite different types were obtained, both possibly originating with loss of the small VII-Itranslocation chromosome. One was isolated when the selective marker in repulsion to T1(I;VII) was used and, without being homo- or hemizygous for the selective marker, it produced stable sectors homozygous for this marker. The other was obtained from both coupling and repulsion diploids and showed a near-diploid genotype; it produced practically only haploid stable sectors of the type expected from monosomics, 2n-1 for the short translocation chromosome.

Aspidistra revoluta, a new species from limestone areas in Chongqing, China

Phytotaxa ◽  
2016 ◽  
Vol 257 (3) ◽  
pp. 280 ◽  
Author(s):  
Hao Zhou ◽  
Si-rong Yi ◽  
Qi Gao ◽  
Jie Huang ◽  
Yu-jing Wei
Keyword(s):  
New Species ◽  
Chromosome Number ◽  
Average Length ◽  
Chromosome Complement ◽  
Pollen Grains ◽  
The Other ◽  
Morphological Comparison ◽  
Chongqing Municipality ◽  
Karyotype Asymmetry ◽  
A New Species

Aspidistra revoluta (Asparagaceae) is described and illustrated as a new species from limestone areas in southern Chongqing Municipality, China. The new species can be distinguished from the other Aspidistra species by its unique umbrella-like pistil with large revolute stigma lobes that bent downwards and touch the base of the perigone. A detailed morphological comparison among A. revoluta, A. nanchuanensis and A. carnosa is provided. The pollen grains of A. revoluta are subspherical and inaperturate, with verrucous exine. The chromosome number is 2n = 38, and the karyotype is formulated as 2n = 22m + 6sm + 10st. The average length of chromosome complement is 4.50 μm, and the karyotype asymmetry indexes A1 and A2 are respectively 0.37±0.03 and 0.49±0.01.

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