Asunto(s)
Animales , ADN , Femenino , Humanos , Masculino , Morfogénesis , Especificidad de la EspecieAsunto(s)
Genética/historia , Austria , Evolución Biológica , Historia del Siglo XX , Selección GenéticaAsunto(s)
Evolución Biológica , ADN/genética , Ambiente , Biología Molecular , Fenotipo , Adaptación Fisiológica , Animales , Regulación de la Expresión Génica , Genes/genética , Genes Homeobox/genética , Variación Genética , Genotipo , Humanos , Morfogénesis , Familia de Multigenes , Mutación , Selección Genética , Especificidad de la EspecieRESUMEN
Each part of a living organism contains a concealed totality which can eventually express itself partially or totally. The extent of the expression is spatially and temporally defined by the morphogenetic field and the environment. Neither the field nor the genome are evolving units. Evolution is produced by the boundary conditions and results in progressive losses, to which the organisms responds. Genetic losses can stabilize the new balance. A living system can be fruitfully compared to a semiotic system.
Asunto(s)
Evolución Biológica , Animales , ADN , Ambiente , Humanos , MorfogénesisRESUMEN
Hyphae from mixed cultures of complementary auxotrophs of Streptomyces coelicolor A3(2) did not grow on minimal media (MM) when fertility plasmids ( SCP1 and SCP2) were missing in both strains. The addition of one part per cent of complete medium (CM) to MM allowed growth of vigorous colonies among the tiny colonies of the parental types. The former, amounting to 1%-10% of the total population, turned out to be heterokaryons. They could be propagated on the same medium by plating of hyphal fragments. When five parts per cent of CM were added to MM, beside the heterokaryotic colonies, vigorous 'spindles' of aerial mycelium were formed whenever complementary colonies overlapped. When the SCP1 and SCP2 plasmids were present in one or both parents a clear constraint on the outburst of heterokaryotic aerial mycelium was observed.
Asunto(s)
Streptomyces/fisiología , Medios de Cultivo/farmacología , Plásmidos , Recombinación Genética , Streptomyces/genética , Streptomyces/crecimiento & desarrolloRESUMEN
Chloramphenicol resistance (Cmlr) of Streptomyces coelicolor A3(2) behaves like a transposon locus, not being localisable in any region of the map and yet being transferable in crosses at a rate comparable to that of chromosomal markers. It can also be transposed onto a plasmid (SCP1) and back to the chromosome. Some traits, such as arginino-succinate synthase production (ArgG), aerial mycelium formation (AmyA), resistance to tetracycline and to rifamycin C appear to be joined to Cml in three processes: co-mutation, i.e. simultaneous loss, post-mutation, i.e. spontaneous loss at high frequency in subclones from Cmls strains, co-transfer, i.e. joint transfer with the cml locus in crosses or during infection by the aggregate SCP1::SCTn1 plasmid. All these processes have been consistently observed with special attention to the argG locus.