Spermatogonial and meiotic chromosomes of the Armenian hamster, Cricetulus migratorius

Lavappa, K. S.; Yerganian, George

doi:10.1016/0014-4827(70)90270-3

Cited by 32 publications

(6 citation statements)

References 10 publications

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“…This pattern is well known in the mouse (Mus musculus) (Solari, 1969;Solari, 1970;Glamann, 1986). While the fixed length of the SC in the armenian hamster may be related to the special paracentromeric chiasmatic localization and composite structure of these chromosomes (Lavappa & Yerganian, 1970), the usual occurrence of desynapsis in most XY mammalian pairs suggests that the partial SC is especially labile. There are hints that suggest that the SC structure is by itself a dynamic structure in constant flux involving continuous assembly and dismantling.…”

Section: The Dynamic Nature Of Xy Synapsismentioning

confidence: 97%

Synaptic behaviour and recombination nodules in the human XY pair

Solari

1988

Genetica

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A sample of 90 XY pairs from men with normal karyotypes has been analyzed by measuring their morphological features in electron micrographs of microspread spermatocytes. The classification of human XY types (Solari, 1980) has been given stricter definitions. Stepwise splitting of the axes is seen in types 1 and 2. The development of axial branches and lengthening of the X axis is seen in type 3. In the two subtypes a and b of type 4 the net-like filamentous array grows in length to a maximum (average = 59.7 microns) in subtype b. The location of the putative Y kinetochore defines a short arm that measures 22.34% of Y axis length, and the kinetochore of the X axis defines a short arm of 38.15% of the axial length. The average number of excrescences in the X axis is 19.9 and in the Y is 4.3. The frequency of a non-homologous, distal end-joining grows steadily from type 0 to type 3. The average length of the synaptonemal complex (SC) in 51 XY pairs of types 1 and 2 is 1.33 microns (SD = 0.65) and it corresponds to 25.54% of the Y axis length. Thus, the average SC covers the short arm of the Y and the pericentromeric region. Maximum lengths of this SC may reach up to 81.8% of the Y axis. 30 recombination nodules (RNs) were located in 26 XY pairs, and 90% of the nodules are located in the distal half of the short arm of the Y axis. Thus, RNs are restricted to a segment much shorter than the length of the average SC. A gradient of decreasing probability of recombination may reach up to the centromeric region of the Y chromosome. Some possible consequences of these facts are discussed.

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Section: The Dynamic Nature Of Xy Synapsismentioning

confidence: 97%

Synaptic behaviour and recombination nodules in the human XY pair

Solari

1988

Genetica

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“…large X and a small Y (Fredga, 1970). On the other hand, chiasmatic associations in XY pairs are found in some of the species having large X and Y chromosomes, as in the Chinese hamster Cricetulus griseus (Fredga & Santesson, 1964) and in the Armenian hamster Cricetulus migratorius (Lavappa & Yerganian, 1970). In other species with large X and Y chromosomes their association is less distinct and the sex chromosomes may appear separated from each other, as in Microtus agrestis (Fredga, 1970).…”

Section: Introductionmentioning

confidence: 94%

Asymmetry and resolution of the synaptonemal complex in the XY pair ofChinchilla laniger

Solari

Rahn

1985

Genetica

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The meiotic behavior of the XY pair of the chinchilla (C. laniger), has been studied with C-banding and with the microspreading procedure for synaptonemal complex (SC) karyotyping. The large X chromosome of the chinchilla has a paracentromeric and two subterminal (stl and st2) C+ bands, while the minute Y chromosome has a C+ long arm. At metaphase-I the X chromosome is associated end-to-end with the short arm of the Y chromosome. The appearance of the X axis in microspread spermatocytes is delayed up to early pachytene. The X axis, as well as the Y axis appear as thick, separated threads. The thick X and Y axes are then co-aligned without forming a SC. The Y axis becomes thinner and then an asymmetrical SC is formed between the axes. This SC becomes symmetrical by a later thinning of the corresponding part of the X axis. During mid-pachytene an additional SC is formed at the other end of the XY pair in many cells. During late pachytene the SCs become resolved and finally the four termini are separated from 6ach other although they tend to be located in the same region of the nucleus. These observations suggest that the SCs in the XY pair of the chinchilla are formed between non-homologous regions. The presence of non-homologous synapsis suggests that the XY pair of C. laniger is joined by an achiasmatic mechanism, different from the chiasmatic joining usually found in eutherian mammals. The presence of subterminal C+ bands in the X chromosome may be a hindrance for the formation ofa SC during early pachytene. It is concluded that the XY pair of the chinchilla shows an intermediate behavior when compared to that of the sand rat on one side, and that of most mammals having a euchromatic X chromosome, on the other side.

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“…1974: Burgoyne, 1982Polani. 1982), although cytological evidence for this phenomenon has been dem onstrated only in a few species, e.g., hamster (Fredga, 1970;Lavappa and Yerganian. 1970), Suncus murinus (Raman and Nanda, 1986), and Sxr mice (Evans et al, 1982).…”

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confidence: 99%

Achiasmatic sex chromosomes in <i>Pitymys duodecimcostatus</i>: mechanisms of association and segregation

Carnero

Jiménez²,

Burgos³

et al. 1991

Cytogenet Genome Res

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The meiotic behavior of the sex chromosomes of Pitymys duodecimcostatus was studied by electron microscopy of whole-mount synaptonemal complex preparations. The results established that the sex chromosomes of this species are achiasmatic and remain unassociated throughout meiotic prophase I in most spermatocytes. In other cells, nonspecific association of the X and Y occurred by means of filamentous bridges. Pitymys duodecimcostatus represents an additional example of a mammalian species lacking a homologous pairing segment in its sex chromosomes and extends current knowledge about this controversial subject. In this regard, we suggest that sex-chromosome association is a characteristic that probably followed different evolutionary paths in different mammals, leading to loss of the homologous segment in some species and its conservation in others. It is also suggested that in P. duodecimcostatus, and probably in many other species as well, three mechanisms may act in concert to permit joining of the X and Y chromosomes during meiotic prophase, and, consequently, to ensure proper segregation during anaphase I: (1) joining of the sex-chromosome axes at their ends to the nuclear membrane, (2) formation of fibrillar structures to hold the sex chromosomes together, and (3) cohesiveness due to sex-vesicle formation.

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Spermatogonial and meiotic chromosomes of the Armenian hamster, Cricetulus migratorius

Cited by 32 publications

References 10 publications

Synaptic behaviour and recombination nodules in the human XY pair

Synaptic behaviour and recombination nodules in the human XY pair

Asymmetry and resolution of the synaptonemal complex in the XY pair ofChinchilla laniger

Achiasmatic sex chromosomes in <i>Pitymys duodecimcostatus</i>: mechanisms of association and segregation

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