Pachytene Bivalents Research Articles

Study of human male meiosis II-Q-banding in pachytene bivalents

In continuation of the research on male human meiosis within the study of pachytene bivalents, results from the analysis of 125 cells are presented. The aim of this work is to establish Q-banding patterns and make a detailed study of chromomere counting and distribution. To obtain Q-bands Quinacrine and Pseudoisocyanine staining techniques have been used.

Pachytene morphology of Sorghum nitidum chromosome complement.

The detailed morphology of the pachytene chromosomes of Sorghum nitidum with one accessory chromosome (2n=10A+1B) has been analyzed. The characteristics of each of the five pachytene bivalents in the haploid complement and the pachytene accessory chromosome are identified on the basis of total length, arm ratio, and the extent of the heterochromatic region. Based on the data derived from the pachytene analysis, the possible origin of the accessory chromosome is discussed.

Identification of the trisomic series in diploid Solanum tuberosum L., group tuberosum. I. Chromosome identification

The morphology of 12 pachytene bivalents of the dihaploid Solanum tuberosum cv. Gineke is described, and the morphological features which are helpful for a critical chromosome identification are illustrated. The difficulties of identifying the individual chromosomes and the extra chromosomes in trisomics are discussed.

Pachytene mapping of the male Chinese hamster.

Minced seminiferous tubules of male Chinese hamsters when treated with a mixture of trypsin (one part) and McCoy's 5a growth medium with 20% fetal calf serum (nine parts) at 4 degrees C, washed twice with the regular growth medium, incubated at 37 degrees C in growth medium for 4 h, and harvested without Colcemid and hypotonic pretreatments, gave excellent pachytene morphology for studies on chromomere patterns. The Giemsa banding patterns of all somatic metaphase chromosomes except the sex chromosomes of the hamster cells correspond well to the chromomere patterns of meiotic pachytene bivalents.

Mitotic and Meiotic Chromosomes ofIchthyophis OrthoplicatusTaylor (Amphibia: Gymnophiona)

SUMMARYMitotic and meiotic chromosomes were studied in an Asian caecilian, Ichthyophis orthoplicatus, by a blood culture method and by spermatocyte squashes. For this species, 2N=42, which is the highest chromosome number in the Order Gymnophiona. The karyotype consists of two large metacentrics, one medium-sized submetacentric, three medium-sized metacentrics, two small metacentrics, one small submetacentric, one small subtelocentric, and eleven telocentric microchromosomes. No heteromorphic pair of sex chromosomes is present in either sex. The 21 spermatocyte bivalents have a variable number of chiasmata, positively correlated with chromosome length. The largest bivalent frequently has four or five chiasmata. There are no ring-shaped bivalents. Observations of pachytene bivalents showed a heteropycnotic rod on the end of one arm of bivalent No. 1, and showed that the nucleolus organizer is on chromosome No. 3.If current concepts of caecilian systematics are correct, then primitive caecilians have high numbers of chromosomes including microchromosomes, and advanced caecilians have reduced chromosome numbers and few or no microchromosomes. This same relationship is known for Anura and Urodela. Asian ichthyophiids are karyotypically similar to Asian and African caeciliids, especially in regard to the large-sized and medium-sized chromosome groups. Neotropical species of Caeciliidae and Typhlonectidae seem to have advanced karyotypes compared to Asian and African forms.

Xylaria polymorpha. II. Cytology of a form with typical robust stromata

The chromosome number of a collection Xylaria polymorpha from England appears to be n = 7, based on counts of pachytene bivalents and metaphase–anaphase chromosomes in ascospores. Ascospores are uninucleate when formed, becoming binucleate by a mitosis. One of the two nuclei is cut off into a cellular appendage. The appendage and its nucleus disintegrate in the ascus before ascospore maturation. Mature ascospores are unicellular and usually show no evidence of the former appendage.

Identification of pachytene bivalents in human male meiosis using G-banding technique.

G-banding of human pachytene bivalents is obtained using trypsin digestion. Each of the 22 autosomal bivalents is clearly identified. Such an identification leads to construction of the human pachytene map. Our results show the equivalence between the G-band patterns of mitotic chromosomes and meiotic bivalents. The G-band patterns of mitotic-meiotic chromosomes also correlate closely with the chromomere sequence of pachytene bivalents. Thus, study of chromomeres should constitute an excellent approach to comprehension of G-banding mechanism.

Scanning electron microscopy of meiotic chromosomes of plants in situ

Scanning electron microscope studies of anthers of the Asiatic Lilium hybrid Enchantment and Solanum tuberosum L. cv. Netted Gem fixed in organic acid – alcohol type fixatives clearly revealed nucleoli, bivalents, and the meiotic spindle. Centromere regions could not be identified in pachytene bivalents, but areas of possible spindle attachment were evident for metaphase I – anaphase I bivalents.

Fine structure of chromosome pairing in ten Ascomycetes: meiotic and premeiotic (mitotic) synaptonemal complexes.

The meiotic prophase of ten Ascomycetes was studied by both light and electron microscopy. All ten species show a “Neurospora type” of meiosis. Two Podospora have no distinct synaptonemal complexes but synaptic structures in their nucleolus. The synaptonemal complexes of the eight other species are well differenciated and have uniform dimensions. The banded pattern of the lateral components seems to be a characteristic of Ascomycetes. The most striking observation is the specificity of this banding which can be used as a marker in interspecific crosses. Ascophanus carneus shows two kinds of synaptonemal complexes: normally between the pachytene bivalents and unusually in the ascogenous hyphae mitoses before meiosis and even before caryogamy.

Ultrastructural analysis of maize pachytene karyotypes by three dimensional reconstruction of the synaptonemal complexes

Aldehyde fixation followed by staining with phosphotungstic acid produces differential contrast between the synaptonemal complex and the chromatin of maize pachytene bivalents. Centromeres, heterochromatic knobs and large chromomeres are easily recognised. With this and other staining techniques the nucleolus organizer region can be differentiated into two components. — Microsporocyte nuclei at pachytene were serially sectioned and all ten bivalents reconstructed in five nuclei. An idiogram was derived from the mean chromosome (= synaptonemal complex) lengths, the arm ratios, positions of knobs and the nucleolus organizer region. The idiogram agrees well with that published from light microscopic analyses. However, bivalent lengths are only two thirds of those observed by light microscopy of squash preparations. Many telomeres of the bivalents are connected via chromatin to the nuclear envelope, but a varying number of free bivalent ends are observed in all five reconstructed nuclei. — Bivalents heterozygous for inversion 3b were reconstructed. In the presence of abnormal chromosome 10 (K10) the lateral components of the synaptonemal complex of chromosome 3 formed a typical inversion loop, while in one of the nuclei having no K10 the two lateral components of the long arms of chromosome 3 remained unpaired in the region of inversion heterozygosity. The presence of K10, which increases crossing-over frequencies and promotes intimate pairing at the light microscopic level, was thus found to permit formation of complete synaptonemal complexes in the inverted region. The extra terminal portion of the K10 chromosome folded back on itself and formed a morphologically normal synaptonemal complex in this — possibly non-homologously paired — region. The chromatin of centromeres and knobs from different bivalents were sometimes found to fuse, but the synaptonemal complexes transversing the fused centromeres or knobs retained their individuality.

Reconstruction of the Neurospora crassa pachytene karyotype from serial sections of synaptonemal complexes.

Serial sections from isolated asci were used to reconstruct the seven pachytene bivalents of Neurospora crassa. The synaptonemal complex could be traced for its whole length in each bivalent, being attached to the nuclear envelope at both ends in six. The satellite end of the nucleolar chromosome did not appear to be attached to the nuclear envelope. The estimated lengths of the bivalents ranged from 10.7 to 5.1 microns in one nucleus, from 11.5 to 4.2 microns in another, and from 8.5 to 4.4 microns in a third, with total haploid complement lengths of 45.5 microns, 47.3 microns, and 43.9 microns respectively. These values are considerably smaller than published light microscopical measurements.—The synaptonemal complex in N. crassa, as in other ascomycetes, has two banded ca. 400 A wide lateral components held about 1200 A apart by a central region containing the ca. 200 A wide central component. With normal glutaraldehyde/OsO4-phosphate buffered fixation the chromatin of the pachytene bivalents is poorly contrasted. Occasional local thickenings of the central component into electron dense nodes ca. 1000 × 500 A in longitudinal section are characteristic of the complex.

Pachytene Karyology of <i>Ipomoea biloba</i>

The entire haploid complement of the pantropical diploid (2n=30) Ipomoea species, I. biloba Forsk has been identified at pachytene stage employing criteria such as relative length, centromere position, nucleolar association, distribution and length of dark- and light-staining segments in the arms and chromomere number, size and pattern of distribution. The diagnostic features of the differentiated pachytene bivalents and the idiogram at this stage are presented. The advantages of pursuing karyological studies at pachytene over that at somatic metaphase in this species is brought out. From a comparative study of pachytene karyotypes of I. biloba and the earlier investigated I. crassicaulis with which it has been recently hybridized, homoeology of eight chromosomes could be adduced. The need for pachytene analyses in this inter-specific hybrid, other releated species and their hybrids is emphasized. Later stages of meiosis were found to be normal leading to formation of over 95% stainable pollen.

Identification and chromomeric interpretation of pachytene bivalents from Canis familiaris.

Squash techniques were used to spread, the 39 pachytene bivalents from spermatogenic Canis familiaris cells collected by testicular biopsy from normal, healthy male collie dogs. Eight cells in which all bivalents could be identified were photographed, enlarged to 4500 × and cutouts prepared for each chromosome in each of the cells. Characterization and identification were based on relative length, mean percentage length, and number of chromomeres in each bivalent.

Morphology of the Pachytene Chromosomes and Meiosis in <i>Manihot esculenta</i> Crantz

Detailed analyses of chromosomes at pachytene and later stages of meiosis were made in a cultivated type of cassava. Pachytene chromosomes are depicted on the basis of total length, relative length, arm ratio, amount and distribution of heterochromatin and number and position of chromomeres. Idiograms showing details of all the eighteen pachytene bivalents in the haploid complement are presented and based on the average values of lengths obtained by accurate measurements of the bivalents in a minimum of 15 completely analyzable nuclei, the eighteen pachytene bivalents have been arranged and numbered in order of their decreasing length as chromosome I to chromosome XVIII. The haploid chromosomal complement, inter alia, has three functional nucleolar chromosomes and six chromosomal types represented in duplicate. Based on the data of the pachytene karyology obtained, a segmental allopolyploid origin of the present day cultivars of cassava has been suggested.Based on cytological data, it has been suggested that meiotic abnormality is not the cause of pollen degeneration in the material studied.

Meiosis in the male of Puto albicans (Coccoidea-Homoptera).

Cytologically, Puto has proved more primitive than its taxonomic position would indicate. In the single previously described example (Hughes-Schrader, 1944), an uncomplicated inverted meiotic sequence was described for the males. The present example, P. albicans, showed a significantly more primitive inverted sequence. Unlike the other examples reported for aphids and coccids, the chromatids of the dyads neither dissociated nor reassociated during interkinesis. Instead, they remained closely associated and interconnected by an unresolved terminal chiasmate attachment. At first metaphase, the spindle attachments were localized to a restricted region of the poleward surface of the chromatids. Localization of attachment during meiosis and close association of chromatids during interkinesis are both suggestive of similar but not identical conditions expected in ancestors with an uninverted meiotic sequence. A second species proved intermediate between P. albicans and that described by Hughes-Schrader in which a complete cycle of dissociation and reassociation occurred during interkinesis. In P. albicans the pachytene bivalents showed no structures suggestive of centric localizations. At their greatest condensation at first metaphase, the chromatids were clearly subdivided into half chromatids. Limited observations were made on chromosomes of other species of Puto and of Phenacoleachia zealandica, and also on spermiogenesis and mycetocyte formation in Puto. The discussion is devoted to considerations of chromatid subdivision, holokinetic chromosomes, and meiotic inversion and some evolutionary implications are mentioned.

THE MORPHOLOGY OF PACHYTENE CHROMOSOMES OF SOME <i>EU-SORGHUMS</i>

The detailed morphology of the pachytene chromosomes and microsporogenesis have been studied in the six Eu-Sorghums. The pachytene chromosomes are depicted on the basis of total length, relative length, arm ratio, amount and distribution of heterochromatin and number and position of chromomeres. The characteristics of each of the ten pachytene bivalents in the haploid complement are described in detail bringing out similarities and differences amongst them. Based on the idiograms of the pachytene chromosomes, the possible role of chromosomes in speciation and the relationship amongst these Eu-Sorghums are discussed. Two basic archetypes in the 20-chromosomed taxa have been suggested-one with five long chromosomes and the other with five short chromosomes. It is proposed that the present day cultivated forms of Eu-Sorghums are allopolyploids of crosses between two such forms.

PACHYTENE CHROMOSOMES OF THE INTERGENERIC HYBRID LYCOPERSICON ESCULENTUM x SOLANUM LYCOPERSICOIDES

Menzel, Margaret Y. (Florida State U., Tallahassee.) Pachytene chromosomes of the intergeneric hybrid Lycopersicon esculentum X Solanum lycopersicoides. Amer. Jour. Bot. 49(6): 605–615. Illus. 1962.—Pachytene bivalents of the hybrid were compared with those of the parents to determine whether the chromosome differentiation assumed to underlie chiasma failure and sterility of the F1 and preferential pairing in the corresponding amphidiploid was reflected in visible differences or failure of synapsis between homeologues. The total pachytene complement length of S. lycopersicoides Dun. was nearly 1.5 times that of the ‘Pearson’ tomato parent; the complement of the hybrid was of intermediate length. Pairing in the hybrid showed that the chromosomes of the parents were visually similar and completely synapsed in 43 of the 47 identifiable regions into which the pachytene complement may be divided. The similar regions included all 23 distal, achromatic segments in which chiasmata were localized, and 20 of the proximal, chromatic segments. The other 4 chromatic segments differed in length and hence exhibited a “deficiency” configuration. According to Barton's system of numbering, these were the short (nucleolar) arm of chromosome 2, the proximal segments of the long arms of chromosomes 4 and 9, and the proximal segments of the short arm of chromosome 10. Sporadic inversion, deletion and translocation configurations found in about 1–5% of pachytene nuclei of the hybrid probably represented newly‐arisen spontaneous aberrations rather than constant differences between the parental genomes. No evidence was found that the chromosomes of the parents differed by small structural rearrangements. Either the rearrangements were below the resolving power of the methods employed, or differentiation has affected some property or properties of the chromosomes other than linear order. Evidence from metaphase I suggested that inequalities in chromatic regions of hybrid bivalents inhibited chiasma formation in adjacent achromatic segments but enhanced it in achromatic segments of the opposite arm. The mean number of bivalent arms having chiasmata at metaphase I was nearly as high in the hybrid as in the ‘Pearson’ parent Univalents at metaphase I in the hybrid result not from failure of synapsis or lowered chiasma frequency but from an unbalanced distribution of chiasmata among the chromosome arms.

Chromosome Behaviour during Spermatogenesis of <i>Anopheles stephensi</i> Sensu Stricto

1. The testes of Anopheles stephensi sensu stricto are two pale yellowish, ellipsoidal bodies. Their wall consists of an outer, tough, pigmented envelope, and an inner squamous epithelial layer. The nuclei of various types of resting cells within the testes are characterized by a peripheral, basophilic crescent. The anterior part of the testicular cavity is divided into cysts which hold spermatogonia and primary spermatocytes. Germ cells at later stages of differentiation are held free within the posterior part of the testicular cavity.2. The spermatogonial metaphase configuration consists of two pairs of V-shaped autosomes and a pair of unequal, subtelocentric sex chromosomes. The homologous chromosomes exhibit somatic pairing. The centromeres appear as distinct, non-staining gaps. The centromere is slightly off-median in one of the autosomal pairs.3. The nuclei of early primary spermatocytes show long, slender, chromomeric threads and a peripheral basophilic crescent. The latter subsequently resolves into deeply staining thread-like structures representing the heterochromatic regions of the sex chromosomes and a lightly staining nucleolar body. The chromosomal threads undergo a process of uniform condensation to produce thick pachytene bivalents. The nucleolus disappears by diplotene. The sex chromosomes associate together only along short lengths of their long limbs proximal to their centromeres. Terminalization of chiasmata takes place during diakinetic condensation of the chromosomes. The sex bivalent is symmetrical. The metaphase spindle is formed within a welldefined nuclear space surrounded by a thin limiting membrane. Tiny dotlike centrioles are present. At first anaphase the autosomal univalents disjoin normally. The sex chromosomes, on the otherhand, show obligatory postreduction. The sex chromosomes lag during the first anaphase separation. In the dyads the chromatids are widely divergent except near the centromere. The telophase nuclei are oval in shape and show a peripheral concentration of chromatin.4. A short interkinesis stage is present. At the second prophase the dyads appear as typical X or cross-shaped figures. Subsequently they constitute a tangled group at the centre of nucleus representing a prometaphase stage. A second metaphase plate is produced although the stage is of short duration only. The sex chromosomes show precession during the second anaphase. The spermatid nuclei fall into two classes on the basis of the relative dimensions of their heteropycnotic dots.