The karyotype of the rainbow trout is characterized by a primitive XX/XY sex-determining chromosomal system. (Thorgaard et al., 1977). In the present study using FISH we have physically linked the 5S rRNA genes to the partially undifferentiated X chromosome pair. PCR amplified 5S rDNA was used for FISH and hybridization signals indicated that the genes were duplicated, present in one acrocentric and one metacentric pair of chromosomes. After analyzing several individuals, the female metaphases showed four fluorescent signals whereas males presented only three signals. Two of the three signals obtained in males corresponded to the metacentric pair whereas the single signal was mapped to the heterochromatin that cytologically differentiates the X chromosome from the Y chromosome. Double FISH experiments demonstrated that the 5S rDNA which is not sex linked is located at the NOR bearing arm close to the major ribosomal RNA genes (5.8S, 18S and 28S), similar to the situation observed in Atlantic salmon (Pendas et al., 1994a).

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In a sporadic case of autism and language deficit due to auditory processing defects, molecular genetic studies revealed that a chromosomal deletion occurred in the 13q12→q13 region. No chromosome abnormalities were detected in the parents. We determined that the deletion occurred on the paternally derived chromosome 13. There are two previous reports of chromosome 13 abnormalities in patients with autism. The deletion in the subject described in this paper maps between the two chromosome 13 linkage peaks described by Bradford et al. (2001) in studies of subjects with autism and language deficits. The 9-Mb region deleted in the patient described here contains at least four genes that are expressed in brain and that play a role in brain development. They are NBEA, MAB21L1, DCAMKL1 and MADH9. These genes therefore represent candidate genes for autism and specific language deficits.

Although the use of the Internet is generalised, its potential as a teaching tool is rarely taken into account. At the same time, there exists a digital divide affecting vulnerable or disadvantaged groups: students of foreign origin and students with special educational needs. It is necessary to identify how inequality can be overcome to reach the objectives set by the United Nations regarding sustainable forms of development for education and to foster more inclusive and egalitarian societies. In this research with students aged 12–16, the objective was to establish profiles according to gender, social class, ethnic background and educational special needs. We used a mixed methodological design, applying a questionnaire to 2734 students from 15 centres and qualitative data collection techniques. We made a descriptive and inferential analysis (SPSS program) and a qualitative data content analysis supported by the “Maxqda” program. The results show that, although most students have Internet access, students of foreign origin and students with special educational needs use this resource less frequently. There are significant differences for gender. Likewise, social divide has an impact on the learning potential of the Internet. Some proposals for improvement are provided, from the framework of the school, with a view to improving socio-educational equity and inclusion in societies in search of a more sustainable form of development.

En este trabajo se presentan los resultados de una investigación realizada con la finalidad de valorar la participación en las redes sociales del alumnado de 3º y 4º de Educación Secundaria (ESO). El objetivo ha sido conocer el acceso y uso que efectúan en su vida cotidiana y las diferencias que se aprecian en función del género, origen (autóctono-extranjero) y necesidad específica de apoyo educativo (NEAE). El diseño metodológico ha sido mixto aplicando un cuestionario tipo Likert, con cinco opciones de respuesta, a 2734 alumnos de 15 centros en la Comunidad Autónoma de la Región de Murcia y complementada con la aplicación de la técnica “Phillips 66”. Los resultados indican que el acceso a las redes sociales es mayoritario, aunque menor en el alumnado extranjero y con necesidad específica de apoyo educativo (NEAE). La participación no está orientada únicamente a intereses personales, sino a necesidades sociales afectivas y relacionales, destacando el entretenimiento, la presencia de amigos y la necesidad de conocer gente nueva. No existe una percepción negativa sobre su consumo que influya desfavorablemente en las tareas de estudio, ocio y relación personal. Se aprecian diferencias significativas entre el alumnado relacionadas con la percepción que tienen sobre la mejora de las relaciones con los amigos debido al uso de las redes sociales, donde se identifica un sentimiento más negativo del alumnado con NEAE, mientras que el alumnado extranjero las utiliza, principalmente, para conocer gente nueva. En cuanto al género, son ellas las que llevan más tiempo participando con la finalidad primordial de contactar con quienes no ven, manifestando tener discusiones con amigos y familia por su uso, y reconociendo tener más preocupación ante la posibilidad de no utilizarlas.