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The
surface-spreading synaptonemal complex (SC) technique was used to
visualize the process of chromosome synapsis in white sturgeon
spermatocytes. Pachytene nuclei had various numbers of univalents (0-3)
and self-paired foldback elements with no obvious centromeric region (1-7)
that may represent accessory chromosomes. The total SC length was 482 (±56)
mm and the average number of SC elements per nucleus was 139 (±3.4). This
SC number suggests a higher chromosome number than had been reported in
previous mitotic studies (2n = 248 ± 8). There was variation in
the SC count both within and between animals. A representative SC
karyotype is presented and some differences between the mitotic and
meiotic karyotypes for this species are discussed. There was no evidence
of multivalent formation, suggesting that the process of diploidization
has gone to completion in the males of this ancient polyploid species.
Each SC had lateral elements of equal length, and no bivalent exhibited
the atypical pairing behavior that is often characteristically associated
with heteromorphic sex chromosomes, suggesting that the male is not the
heterogametic sex in white sturgeon.
Genome,
41:
51-61 (1998)
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