RESUMEN
In meiotic prophase I, chromatin fibrils attached to the lateral elements of the synaptonemal complexes (SC) form loops. SCAR DNA (synaptonemal complex associated regions of DNA) is a family of genomic DNA tightly associated with the SC and located at the chromatin loop basements. Using the hybridization technique, it was demonstrated that localization of SCAR DNA was evolutionarily conserved in the isochore compositional fractions of the three examined genomes of warm-blooded vertebrateshuman, chicken, and golden hamster. The introduction of the concept of the comparative loops (CL) of DNA that form of chromatin attach to SC in the isochore compositional fractions provided the calculation of their length. An inverse proportional relationship between the length of CL DNA and the GC level in the isochore compartments of the studied warm-blooded vertebrate genomes was revealed. An exception was the GCpoorest L1 isochore family. For different compositional isochores of the human and chicken genomes, the number of genes in the CL DNA was evaluated. A model of the formation of GC-rich isochores in vertebrate genomes, according to which there was not only an increase in the GC level but also the elimination of functionally insignificant noncoding DNA regions, as well as joining of isochores decreasing in size, was suggested.
Asunto(s)
Cromatina , ADN , Meiosis , Modelos Biológicos , Profase , Complejo Sinaptonémico , Animales , Pollos , Cromatina/genética , Cromatina/metabolismo , Cricetinae , ADN/genética , ADN/metabolismo , Humanos , Complejo Sinaptonémico/genética , Complejo Sinaptonémico/metabolismoRESUMEN
Here we report a rapid and cost-effective method for the extraction of total DNA from herbarium specimens up to 50-90-year-old. The method takes about 2 h, uses AMPure XP magnetic beads diluted by PEG-8000- containing buffer, and does not require use of traditional volatile components like chloroform, phenol, and liquid nitrogen. It yields up to 4 µg of total nucleic acid with high purity from about 30 mg of dry material. The quality of the extracted DNA was tested by PCR amplification of 5S rRNA and rbcL genes (nuclear and chloroplast DNA markers) and compared against the traditional chloroform/isoamyl alcohol method. Our results demonstrate that the use of the magnetic beads is crucial for extraction of DNA suitable for subsequent PCR from herbarium samples due to the decreasing inhibitor concentrations, reducing short fragments of degraded DNA, and increasing median DNA fragment sizes.
Asunto(s)
Asteraceae/química , Asteraceae/genética , Botánica/métodos , ADN de Plantas/aislamiento & purificación , Técnicas Genéticas , Cloroformo/química , ADN de Plantas/análisis , ADN de Plantas/metabolismo , Fluorometría , Técnicas Genéticas/economía , Pentanoles/química , Hojas de la Planta/química , Hojas de la Planta/genética , Polietilenglicoles/química , Reacción en Cadena de la Polimerasa , ARN Ribosómico 5S/genética , Ribulosa-Bifosfato Carboxilasa/genética , EspectrofotometríaRESUMEN
In meiotic prophase I attached to the lateral elements of the synaptonemal complex chromatin fibrils form loops. SCARs DNA (Synaptonemal Complex Associated Regions of DNA) is a family of genomic DNA sequences tightly associated with the synaptonemal complex and lying at the loop basements. Isochore compositional fractions of the human and chicken genomes were used as 32P-labeled probes for hybridization with the SCARs DNA isolated previously from the spermatocyte nucleus of the golden hamster Mesocricetus auratus. The localization of sequences, similar to golden hamster SCARs DNA in the human and chicken genome isochores was established. It was concluded that SCARs DNA localization into isochore com- partments of examined genomes is evolutionary conservative.
Asunto(s)
Secuencia Conservada , Evolución Molecular , Isocoras/genética , Complejo Sinaptonémico/genética , Animales , Pollos , Cricetinae , Humanos , Masculino , Mesocricetus , Espermatocitos/metabolismo , Complejo Sinaptonémico/metabolismoRESUMEN
Synaptonemal complex (SC) is a specific structure for prophase I of meiosis. Recently we have described synaptonemal complex tightly associated regions of DNA (SCARs DNA) as a particular family of genomic DNA. Now we reveal the evolutionary conservation of SCAR DNA sequences of vertebrates. This data correlates with universal morphology of SCs and similar processes proceed in prophase I of meiosis at representatives of different taxa.
Asunto(s)
ADN/genética , Evolución Molecular , Profase Meiótica I/fisiología , Complejo Sinaptonémico/genética , Animales , CricetinaeRESUMEN
The synaptonemal complex isolated from the spermatocyte nuclei by exhaustive hydrolysis of the latter by DNase II contains tightly associated DNA sequences (SCAR DNA). Here we studied the compositional properties of a cloned family of SCAR DNA of golden hamster, namely we performed the localization of 27 SCAR DNA clones on compositionally fractionated genomic DNA from golden hamster. We observed that sequences of the SCAR DNA family are mainly localized in the GC-poor isochore families L1 and L2, that showed 63% hybridization signals. This means that 37% of signals is referred to the GC-rich isochores, indicating the presence of SCAR DNA overall the genome, even if each isochore family presents differences in density and sequence type. Moreover, the SCAR DNA sequences containing regions of homology with LINE/SINE repeats were observed in all the isochore families. The compositional localization of SCAR DNA is in agreement with the hypothesis that SC and SCAR DNA participate in the chromatin organization during the meiosis prophase I, which should result in the attachment of chromatin loops to lateral elements of SC along the whole length of the latter.