FISH detection of ribosomal cistrons and assortment-distortion for X and B chromosomes in Dichroplus pratensis (Acrididae)

• Published in: Cytogenetic and genome research Vol. 106; no. 2-4; pp. 295 - 301
• Main Authors: Bidau, C.J., Rosato, M., Martí, D.A.
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland S. Karger AG 01.01.2004
• Subjects: Acrididae; Animals; Chromosomal Instability - genetics; Chromosomes - genetics; DNA, Ribosomal - genetics; Female; Genes - genetics; Grasshoppers - genetics; In Situ Hybridization, Fluorescence - methods; Male; Meiosis - genetics; Meiotic Prophase I - genetics; Melanoplinae; Nucleolus Organizer Region - genetics; Ribosomes - genetics; Spindle Apparatus - genetics; Structure and Origin of B Chromosomes; X Chromosome - genetics
• ISBN: 3805578075; 9783805578073
• ISSN: 1424-8581; 1424-859X
• DOI: 10.1159/000079302

Assortment-distortion with respect to the X and NOR activity of a rare mitotically stable B chromosome (B N ), was examined in 16 males of Dichroplus pratensis (Acrididae: Melanoplinae) from Argentine populations. In 1B individuals, the X and B associate preferentially during prophase I reaching a maximum level of association at zygotene. Frequency of X/B association remains relatively high up to diplotene-diakinesis and decreases steeply towards metaphase I. The percent X/B association at each stage is positively influenced by association at the previous stage, and interindividual variability in X/B association decreases as the frequency of association increases. Both chromosomes tended to preferentially orientate toward the same pole at MI (mean ratio of 16 individuals, 1.50:1) which determined an excess of XB and 00 second spermatocytes over X0 and 0B ones (1.39:1). No significant differences occurred between the MI, AI and MII assortment ratios. Fluorescent in situ hybridisation (FISH) confirmed that the B chromosome carries ribosomal genes and helped to establish that, during spermiogenesis, both the B and the normal NOR-bearing chromosome (S 8 ) are clustered near the centriole adjunct region of spermatids. However, FISH failed to reveal the existence of inactive ribosomal cistrons in the X chromosome, as previously suggested, thus providing no support to a simple origin of the B from the X.