Cross-species comparison is an effective tool used to identify genes and study their function in both normal and pathological conditions. We have applied the power of Drosophila genetics to the vast resource of human cDNAs represented in the expressed sequence tag (EST) database (dbEST) to identify novel human genes of high biological interest. Sixty-six human cDNAs showing significant homology to genes causing Drosophila mutant phenotypes were identified by screening dbEST using the "text string' option, and their map position was determined using both fluorescence in situ hybridization (FISH) and radiation hybrid mapping. Comparison between these genes and their putative partners in Drosophila may provide important insights into their function in mammals. Furthermore, integration of these genes into the transcription map of the human genome contributes to the positional candidate approach for disease gene identification.

The distribution of (TTAGGG)n telomeric repeats was studied in chromosomes of two Atlantic eels, Anguilla anguilla and A. rostrata. We found that these sequences hybridize to all the telomeres but also to the entire nucleolar organizer region (NOR) localized in both species at the short arm of chromosome 8. This was considered to be due to the interspersion of telomeric sequences within the NOR ones. Whatever the significance of this interspersion may be, it seems to be limited to A. anguilla and A. rostrata since in Muraena helena (family muraenidae), which also belongs to the Anguilliformes, no telomeric hybridization signals were found along the NOR regions.

Stick insects have been studied mainly for non-conventional reproduction modes, such as parthenogenesis, hybridogenesis and androgenesis. Parallel karyological investigations have evidenced extensive numerical and structural chromosome re-patterning, particularly evident in hybrid parthenogenetic taxa. Chromosome sets of bisexual Leptynia (Pantel) species show an evolutionary trend from 40 to 36 chromosomes and are characterized by cytological satellites of variable size and localization. We performed fluorescence in situ hybridization (FISH) analysis using 45S ribosomal genes and pentameric (TTAGG)n telomere sequences as probes in two strictly related but karyotypically distinct species, L. montana Scali (2n = 38/37; XX/XO) and L. attenuata Pantel (2n = 36). L. attenuata has recently been split into three subspecies (L. attenuata attenuata, L. attenuata iberica and L. attenuata algarvica), and found to share an XX/XY sex chromosome formula, unusual for stick insects. FISH by 45S rDNA sequences consistently labelled the short arm of the 4th chromosome pair, often of a variable size. Silver staining showed that nucleolar organizer regions (NORs) are active. FISH of the telomeric repeats, besides ordinary telomeres, also labelled the short arm of this same pair. The use of both probes in double FISH analysis fully confirmed the co-localization of ribosomal and telomeric highly repeated sequences. Since it is increasingly emerging that the co-localization of NORs and telomeric sequences appears to be a feature shared by evolutionarily distant animals, its possible role is discussed.

We investigated the genetic diversity and connectivity patterns of mesophotic Corallium rubrum populations (from a depth of 87 to 107 m) near Sardinia (Western Mediterranean Sea) using mi- crosatellite data. Firstly, we tested the hypotheses that (1) mesophotic areas represent ‘thermal and/or repro- ductive refugia’ for the species, and (2) strong genetic breaks separate the coral populations of the different sub-basins of the Western Mediterranean Sea. Second- ly, we aimed to examine the impact of harvesting on the genetic features of populations. Genetic analyses pointed out the occurrence of significant genetic differentiation (overall FST = 0.115, P value = 0) and an isolation-by-distance pattern. Bayesian assign- ment analyses revealed four distinct clusters. The differential amplification success of some microsatel- lite loci along a north–south gradient confirmed the existence of strongly differentiated red coral populations in the Tyrrhenian with respect to the Algero-Provenc ̧al Basin. From a management per- spective, the high genetic diversity and the substantial demographic stability indicate that Sardinian red coral populations are stable and still sustainably exploited. Nevertheless, the significant spatial structuring at the scale of less than 10 km indicates that they are sustained largely by local recruitment, excluding the possibility that they can help in recovering shallower bank

Early and late replication bandings have been obtained by in vitro BrdU incorporation in the Mediterranean Muraenidae species Muraena helena and Gymnothorax unicolor, and used to characterize their karyotypes. A comparative analysis of the banding patterns allowed to point out high karyotype similarity as well as chromosome rearrangements that occurred in karyotype evolution between these species.