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Abstract

Spontaneous mutation related to gene methG 1 of Aspergillus nidulans (Mutações espontâneas relacionadas ao gene methG 1 de A. nidulans) Marta dos Santos Baracho*Mutations related to gene methG1 of A. nidulans were analyzed in order to verify if there is a preferential site where these mutations occur, and to study a mathematical model for the determination of the mutation rate per nucleus per generation, in filamentous fungi. A replica plating technique was used to inoculate, in a single operation, 26 colonies of the strain on Petri dishes containing culture medium. But only the nine central colonies were analyzed for size and volume, number of conidia and nuclei in each colony, viability of conidia, size of the conidial heads and number of conidia in each conidial head. Using this technique, 99 central colonies were analyzed with regard to the appearance of mutation and the number and type of reversions were determined for each colony. The frequencies obtained for each reversion were analyzed in order to verify if they followed a Greenwood and Yule distribution. From the data obtained we may conclude that the mutations analyzed occur preferentially in the sterigma and that, by means of the mathematical model studied, it is possible to determine the mutation rate per nucleus, per generation, in filamentous fungi.Research supported by CAPES. Publication supported by FAPESP. Eloisa Auler-Bittencourt*The Philadelphia chromosome (Ph) resulting from a t(9;22)(q34;q11) translocation is a highly specific finding in bone marrow cells of patients with chronic myeloid leukemia (CML), as it occurs in 90 to 95% of cases. In 5 to 10% of cases, the Ph chromosome is involved in more complex rearrangements, producing the same classic molecular change, but not always being identified by traditional cytogenetics, as it may appear as a normal karyotype or as a different rearrangement. The crucial pathogenetic consequence of this translocation is the formation of a hybrid BCR/ABL gene, the product of which is a chimera protein with tyrosine kinase activity. Based on recent evidence, it has been suggested that CML should be defined by the presence of a Ph chromosome (or the BCR/ ABL rearrangement) and that its absence would be consistent with a different myeloproliferative process. The fluorescent in situ hybridization (FISH) method has been used in addition to cytogenetic analysis for the identification of chromosome segments involved in complex rearrangements and has also shown to be a sensitive method for the detection of the BCR/ABL fusion, both in metaphases and in interphase nuclei. Treatment with interferon-alpha (IFN-α) induces hematological remission in 60 to 80% of patients with CML in the chronic phase. Patients in which a significant hematological response is obtained show a greater survival rate than those who do not respond to therapy. For cytogenetic analysis, cells in metaphase are necessary, whereas the FISH technique allows detection and quantitative evaluation of the BCR/ABL fusion in interphase nuclei. In this ...