title: Two-dimensional gel analysis of repetitive nuclear DNA sequences in the genome of Physarum polycephalum. Developmental regulation of the ribosomal gene number.
abstract: The composition of repetitive sequences in restriction patterns of nuclear DNA of Physarum polycephalum was determined by high-resolution gel analysis. Three types of repeated DNA fragments in the size range of (0.2-2) X 10(3) base pairs could be identified as discrete spots on the gels and distinguished by their abundance and above-average base composition of either guanine and cytosine (G + C) or adenine and thymidine (A + T). On comparing the DNA composition from exponentially growing plasmodia with that of starved plasmodia, which have become competent to sporulate and have lost 80% of their nuclei, no change was detected among the (A + T)-rich repeat fractions, whereas several of the (G + C)-rich fractions revealed fewer copies in the DNA prepared from starved cells. As shown by hybridization under saturating conditions, the reduction of several (G + C)-rich repeated sequences in the restricted nuclear DNA in sporulation-competent cells can be explained by a 64% elimination of the extrachromosomal nucleolar ribosomal DNA sequences.
mesh_terms: D001345:Autoradiography; D001482:Base Composition; D002466:Cell Nucleolus / Q000032:analysis; D002467:Cell Nucleus / Q000032:analysis; D003101:Collodion; D004262:DNA Restriction Enzymes; D004271:DNA, Fungal / Q000032:analysis*; D004275:DNA, Ribosomal / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D009693:Nucleic Acid Hybridization; D010804:Physarum / Q000235:genetics* / Q000502:physiology; D012091:Repetitive Sequences, Nucleic Acid; D013172:Spores, Fungal
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D003101:Collodion; D004262:DNA Restriction Enzymes