| Título: | How long did it take for life to begin and evolve to cyanobacteria? |
| Autores: |
Lazcano Araujo Reyes, Antonio Eusebio Miller, SL |
| Fecha: |
20130312T14:38:29Z 20130312T14:38:29Z 1994 |
| Publicador: | Facultad de Ciencias - UNAM |
| Fuente: |
 |
| Tipo: | Artículo de investigación |
| Tema: |
Biochemistry & Molecular Biology Evolutionary Biology Genetics & Heredity Prebiotic synthesis Early gene duplication Time for life to arise |
| Descripción: | There is convincing paleontological evidence showing that stromatolitebuilding phototactic prokaryotes were already in existence 3.5 x 10(9) years ago. Late accretion impacts may have killed off life on our planet as late as 3.8 x 10(9) years ago. This leaves only 300 million years to go freom the prebiotic soup to the RNA world and to cyanobacteria. However, 300 million years should be more than sufficient time. All known prebiotic reactions take place in geologically rapid time scales, and very slow prebiotic reactions are not feasible because the intermediate compounds would have been destroyed due to the passage of the entire ocean through deepsea vents every 10(7) years or in even less time. Therefore, it is likely that selfreeplicating systems capable of undergoing Darwinian evolution emerged in a period shorter than the destruction rates of its components (<5 million years). The time for evolution freom the first DNA/protein organisms to cyanobacteria is usually thought to be very long. However, the similarities of many enzymatic reactions, together with the analysis of the available sequence data, suggest that a significant number of the components involved in basic biological processes are the result of ancient gene duplication events. Assuming that the rate of gene duplication of ancient prokaryotes was comparable to today's present values, the development of a filamentous cyanobacteriallike genome would require approximately 7 x 10(6) yearsor perhaps much less. Thus, in spite of the many uncertainties involved in the estimates of time for life to arise and evolve to cyanobacteria, we see no compelling reason to assume that this process, freom the beginning of the primitive soup to cyanobacteria, took more than 10 million years. |
| Idioma: | Inglés |