Repetitive DNAs in the slug Milax nigricans: association of ribosomal (18S-28S and 5S rDNA) and (TTAGGG)n telomeric sequences in the slug M. nigricans (Mollusca: Gastropoda: Pulmonata).
Spermatocyte chromosomes of the slug Milax nigricans (Mollusca: Gastropoda: Pulmonata) were studied using silver staining (Ag-NOR) and fluorescent in situ hybridization (FISH) with four repetitive DNA probes [18S rDNA, 5S rDNA, (TTAGGG)n and (GATA)n]. Silver impregnation was inadequate to localize the chromosome sites of nucleolus organizer regions (NORs) since no silver dots occurred on the chromosomes at spermatogonial metaphase and a diffuse silver stainability could be observed on the bivalents at metaphase-I. Unlike silver staining, single-colour rDNA FISH consistently mapped major ribosomal sites (18S-28S rDNA) on two small-sized chromosomes in spermatogonial cells and on the correspondent metaphase-I bivalent in spermatocytes. While telomeric (TTAGGG)n sequence hybridized to all chromosomes, (GATA)n probe localized abundant hybridization sites, dispersed throughout the genome. Simultaneous double-colour FISH demonstrated a close chromosomal association of 18S-28S rDNA, 5S rDNA and (TTAGGG)n.
Dipartimento di Biologia Animale, Università di Palermo, Via Archirafi 18, 90123 Palermo, Italy. zuvitcol@unipa.it
R
R
Vitturi
L
L
Sineo
N
N
Volpe
A
A
Lannino
M
M
Colomba
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008974:Mollusca / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012339:RNA, Ribosomal, 28S / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012834:Silver; D013090:Spermatocytes / Q000378:metabolism; D013194:Staining and Labeling; D016615:Telomere / Q000235:genetics
D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012339:RNA, Ribosomal, 28S; D012341:RNA, Ribosomal, 5S; D012834:Silver; D004247:DNA