Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. I. Pachytene karyotype substaging of normal sheep.

Meiotic chromosome pairing behaviour in three normal sheep was surveyed by synaptonemal complex (SC) analysis at the electron microscope level. The SC karyotype of normal rams is composed of a sex pair, three metacentric or submetacentric pairs, and 23 acrocentric autosomal bivalents, with the total autosomal SC length ranging from 309 to 315 μm. Five nucleoli are terminally located on the three metacentric, and one large and one small acrocentric autosomal bivalents. XY morphology was used to divide pachytene into five substages. Although pairing abnormalities (mostly SC interactions) were recorded in an average of 16% of the spermatocytes, bivalent–XY association occurred in only 4.7% of the cells.Key words: sheep, synaptonemal complex, XY pair, pachytene substaging.

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Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. III. Deficient pairing and NOR role in Massey III heterozygotes

Genome ◽

10.1139/g94-114 ◽

1994 ◽

Vol 37 (5) ◽

pp. 802-808 ◽

Cited By ~ 4

Author(s):

K. Dai ◽

C. B. Gillies ◽

A. E. Dollin

Keyword(s):

Synaptonemal Complex ◽

Complex Analysis ◽

Chromosome Rearrangement ◽

Nucleolar Organizer ◽

Ovis Aries ◽

Domestic Sheep ◽

Nucleolar Organizer Regions ◽

Robertsonian Translocations ◽

Synaptonemal Complex Analysis ◽

Pairing Behaviour

Spermatocytes from rams heterozygous for Massey translocation III (t37;25) contained one trivalent and those from the rams heterozygous for both Massey translocations I and III (t1t3) contained two trivalents. Where two trivalents and the XY pair are present in the same nucleus they may form a synaptonemal complex (SC), but no SC segment is found between the two trivalents. The frequency of pairing abnormality in four t3 rams and two t1t3 rams did not significantly differ from that in the normal sheep, but t3 trivalents with diverse abnormal configurations were recorded. A hypothesis was proposed that nucleolar organizer regions (NORs) or nucleoli could account for deficient pairing behaviour and hence chromosome rearrangement, because the NOR region on an NOR-bearing chromosome was usually delayed in pairing, and unpaired regions tended to associate with other unpaired axes or SCs.Key words: Bovidae, NOR, deficient pairing, chromosome rearrangement.

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Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. II. Trivalent and pairing abnormalities in Massey I and Massey II heterozygotes

Genome ◽

10.1139/g94-096 ◽

1994 ◽

Vol 37 (4) ◽

pp. 679-689 ◽

Cited By ~ 5

Author(s):

K. Dai ◽

C. B. Gillies ◽

A. E. Dollin

Keyword(s):

Complex Analysis ◽

Ovis Aries ◽

Domestic Sheep ◽

Robertsonian Translocations ◽

Xy Bivalent ◽

Synaptonemal Complex Analysis ◽

Unpaired Chromosome ◽

Pachytene Spermatocytes ◽

Small Testis ◽

Trisomic Cell

Zygotene and pachytene spermatocytes from Massey I (t1 5;26) and Massey II (t2 8;11) translocation heterozygotes each contained one trivalent, often delayed in pairing, while cells from double Massey translocation heterozygotes had two such trivalents. As meiosis progressed, trivalents became fully paired, with acrocentric axes in a cis configuration. Abnormal pairing configurations often resulted from interactions between unpaired chromosome axes or segments. However, when two Massey trivalents were present in the same nucleus, there was no pairing interaction between them. In different Massey translocation heterozygotes, trivalent-involved pairing abnormalities occurred in 14–28% of cells, with XY–trivalent and XY–bivalent–trivalent associations being as high as 7.1–23.1%. In spermatocytes from single and double Massey translocation heterozygotes with normal-sized testes, the total SC abnormality frequency was 34.4% for the t1 heterozygotes, 27.1% for the t2 heterozygotes, and 21.4% for the double heterozygote. One Massey II heterozygote with one normal and one small testis had significantly higher SC abnormality frequency (54%) than normal rams. A trisomic cell was recorded in one ram and two hyperdiploid cells in another ram, but these were unrelated to the translocations. It is suggested that resolution of pairing abnormalities by synaptic adjustment is important in reducing the effects on fertility of the translocations.Key words: sheep, Robertsonian translocation, trivalent, abnormal pairing configuration.

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Synaptonemal complex analysis of hybrid cattle. I. Pachytene substaging and the normal full bloods

Genome ◽

10.1139/g89-522 ◽

1989 ◽

Vol 32 (5) ◽

pp. 856-864 ◽

Cited By ~ 11

Author(s):

A. E. Dollin ◽

J. D. Murray ◽

C. B. Gillies

Keyword(s):

Electron Microscopy ◽

Synaptonemal Complex ◽

Chromosome Pairing ◽

Complex Analysis ◽

Bos Taurus ◽

Meiotic Chromosome ◽

Early Pachytene ◽

Meiotic Chromosome Pairing ◽

Synaptonemal Complex Analysis

Meiotic chromosome pairing abnormalities in full-blood and hybrid Bos taurus and B. indicus cattle have been surveyed by electron microscopy of pachytene synaptonemal complex spreads. In this paper, the full-blood spreads are described in detail, including the use of XY and nucleolar morphology and other measured parameters for pachytene substaging. Pairing abnormalities were observed in up to 9% of the full-blood spreads. Most of these pairing abnormalities (83%) occurred in early-pachytene spreads, suggesting that the mechanism of synaptic adjustment may operate in cattle.Key words: synaptonemal complex, cattle, pachytene substages.

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Synaptonemal complex analysis of hybrid cattle. II. Bos indicus × Bos taurus F1 and backcross hybrids

Genome ◽

10.1139/g91-035 ◽

1991 ◽

Vol 34 (2) ◽

pp. 220-227 ◽

Cited By ~ 6

Author(s):

A. E. Dollin ◽

J. D. Murray ◽

C. B. Gillies

Keyword(s):

Synaptonemal Complex ◽

Complex Analysis ◽

Bos Taurus ◽

Meiotic Chromosome ◽

Bos Indicus ◽

Backcross Hybrid ◽

Synaptonemal Complex Analysis ◽

Backcross Hybrids ◽

Fertility Problems ◽

And Inversion

The levels of meiotic chromosome pairing abnormalities observed in six Australian F, Bos indicus x Bos taurus cattle crosses (mean = 23%) were significantly higher than those of the full-blood breeds (9%). The abnormal configurations in the F[hybrids included partial pairing failure, multivalents, interlocks, and inversion pairing. Abnormal configurations were also present, but at lower frequency, in backcross hybrid bulls. The main types of abnormal configurations and the levels of XY-autosomal associations and autosomal asynapsis observed were unlikely to cause significant fertility problems in the hybrids.Key words: synaptonemal complex, hybrid cattle, meiosis.

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Quadrivalent formation in a tetraploid chicken oocyte

Genome ◽

10.1139/g88-145 ◽

1988 ◽

Vol 30 (6) ◽

pp. 900-902 ◽

Cited By ~ 5

Author(s):

A. J. Solari ◽

N. S. Fechheimer

Keyword(s):

Electron Microscopy ◽

Synaptonemal Complex ◽

Complex Analysis ◽

W Chromosome ◽

Autosomal Bivalents ◽

Initiation Point ◽

Recombination Nodule ◽

Synaptonemal Complex Analysis ◽

Threshold Length ◽

Pairing Initiation

Synaptonemal complex analysis of an exceptional tetraploid oocyte from a diploid chicken heterozygous for the MN t (Z;1) rearrangement was performed by electron microscopy of a spread preparation. Ten separate quadrivalents (26% of the chromosomal axes) were analyzed, as well as 50 autosomal bivalents. All the axes less than 2.5 μm in length formed bivalents (38) only, while axes in the 2.5–4.2 μm range formed 5 quadrivalents and 12 bivalents. The longer, separate axes formed quadrivalents only. Partner switches in excess of one were documented. The two identical W chromosomes paired only at the ends of their short arms. Quadrivalent formation may require a threshold length (2.5 μm), at least in this species. The tip of the short arm of the W chromosome may be a pairing initiation point, and it corresponds to the region associated with a localized recombination nodule previously described in diploid oocytes.Key words: quadrivalent, tetraploid, synaptonemal complex, chicken oocyte.

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