onwards, the m chromosomes begin to get closer and associate end-to-end to form a pseudobivalent (pII) (Fig.
Because the medial element most frequently remains as a univalent at diakinesis, aneuploidy of at least 31.5% (one-half the frequency of the univalent) is expected.
Configurations observed at diakinesis were consistent with the SC analyses.
Although diffuse-stage nuclei present morphological differences depending on the species studied, it is clear that they always imply an overall change of chromosome organization between pachytene and diakinesis
strictum, revealed that the B chromosomes were detected in the metaphase I and anaphase I, but they were absent in the diakinesis
. The evidence of preferential segregation of B chromosomes in the accession ETB AZ 055 is the reduction of the tetrads and microspore with micronuclei (14.4%) (Figures 1C and E), indicating that the majority of Bs were included in the nuclei to guarantee their propagation or the expulsion from the cytoplasm, therefore originating the microcytes (Figures C and D).
[Indirect evidence of recombinogenic Y-specific regions is available from an XY/XYY mosaic common shrew (Sorex araneus), in which an interstitial chiasma was observed in a YY bivalent from an XYY cell at late diplonema/ early diakinesis
(Searle and Wilkinson, 1986).] If a positive correlation between recombinogenicity and transposable element integration can be established, this would indicate that the structural nature of a particular chromosomal region could also impose constraints upon transposable element accumulation.
(1995) found n=5, which doesn't agree with the cited authors and with our results presented in table 1, where bivalent associations of chromosomes in diakinesis
(n=10) can be observed, therefore the studies accessions possess 2n=20, in this study considered diploid, even though discussion suggest that this is the probable tetraploid level.
The species apparently is a segmental allotetraploid because its chromosomes typically pair as one or two quadrivalents and 16 or 14 bivalents during diakinesis
of meiosis I.
They reported enneavalent (association of three trivalents), hexavalent, pentavalent, and quadrivalent configurations at diakinesis
or Metaphase I.
Ile anthers at diakinesis
or metaphase I were hydrolyzed in 1M HCl for 5 min at WC, rinsed in distilled water then placed in a drop of 2% (w/v) acetocarmine.
Cytological observation of multivalents at diakinesis
and metaphase I indicated that the two cultivars differ by at least one reciprocal chromosome interchange (Leach, 1989).
Consequently, much of the data in Table 2 for this species was obtained from cells at diakinesis
. The overall average chromosome pairing behavior for both accessions was 0.24 univalents + 17.45 bivalents + 1.22 quadrivalents.