Ahp2 (Hop2) function in Arabidopsis thaliana (Ler) is required for stabilization of close alignment and synaptonemal complex formation except for the two short arms that contain nucleolus organizer regions

ABSTRACT Well-synchronized populations of oocytes obtained by means of the "pupal system" (Grell, 1973a) have been examined to determine the time of appearance of the synaptonemal complex. The complex first appears in the most advanced oocytes between 132 and 138 hr of female development. Between 138 and 156 hr the complex apparently undergoes a fourfold increase in length. At 150 and 156 hr the complex system is extensive and present in virtually all oocytes. Previous studies using the pupal system have placed the period of premeiotic DNA synthesis between 132 and 162 hr. Thus, indirect evidence indicates that a significant portion of synaptonemal complex formation is coextensive with the main DNA replication in the oocyte. Direct evidence that DNA synthesis and complex formation occur simultaneously in oocytes has been obtained by electron microscope autoradiography. By definition, then, the stage of synaptonemal complex formation in Drosophila must include premeiotic interphase.

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G-band position effects on meiotic synapsis and crossing over.

Genetics ◽

10.1093/genetics/118.2.307 ◽

1988 ◽

Vol 118 (2) ◽

pp. 307-317

Author(s):

T Ashley

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Chromosomal Rearrangement ◽

Chromosomal Rearrangements ◽

Crossing Over ◽

Position Effects ◽

Band Position ◽

Synaptonemal Complex Formation ◽

Meiotic Synapsis ◽

Nonhomologous Synapsis

Abstract An examination of synaptic data from a series of X-autosome translocations and crossover data from an extensive series of autosome-autosome translocations and autosomal inversions in mice has lead to the development of a hypothesis which predicts synaptic and recombinational behavior of chromosomal aberrations during meiosis. This hypothesis predicts that in heterozygotes for chromosomal rearrangements that meiotically align G-light chromatin with G-light chromatin lack of homology will be recognized. If homologous synapsis cannot proceed, synaptonemal complex formation will cease and there will be no physical suppression of crossing over in such rearrangements. However, if a chromosomal rearrangement aligns G-light chromatin with G-dark chromatin at the time of synapsis, lack of homology will not be recognized and synaptonemal complex formation will proceed nonhomologously through the G-dark chromatin. Crossing over will be physically suppressed in this region and this suppression of crossing over will be confined to the chromosome in which the G-light chromatin is nonhomologously synapsed with G-dark chromatin. When G-light chromatin is once again aligned with G-light chromatin, lack of homology again will be recognized and either homologous synapsis will be reinitiated (as in an inversion loop), or will cease altogether (as in some translocations). Unlike the previously described "synaptic adjustment", this nonhomologous synapsis of G-light with G-dark chromatin appears to compete with homologous synapsis during early pachynema.

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Meiosis in triploid Lolium. I. Synaptonemal complex formation and chromosome configurations at metaphase I in aneuploid autotriploid L. multiflorum

Genome ◽

10.1139/g94-025 ◽

1994 ◽

Vol 37 (2) ◽

pp. 181-189 ◽

Cited By ~ 10

Author(s):

Huw M. Thomas ◽

Barry J. Thomas

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Lolium Multiflorum ◽

Synaptonemal Complexes ◽

Pollen Mother Cells ◽

Partner Exchange ◽

Synaptonemal Complex Formation ◽

Mother Cells ◽

Axial Element ◽

Metaphase I

A spreading technique for synaptonemal complexes (SCs) was applied to pollen mother cells of two aneuploid genotypes of autotriploid Lolium multiflorum (2n = 3x + 1 = 22). In the earliest nuclei analyzed the axial elements are in six groups of 3 and one group of 4. Most groups have formed multivalents with from one to five pairing partner exchanges, but there are also groups that have formed bivalents and univalents. Some axial elements have formed triple associations, in one case for the length of the trivalent. Unsynapsed axial elements remain aligned with their homologous SCs into pachytene, but this alignment is abolished as these axes pair heterologously among themselves until the entire axial element complement is synapsed. At metaphase I most chromosomes are associated as trivalents and quadrivalents.Key words: Lolium, triploid, pairing partner exchange, chiasma, multivalent.

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