--- A cikkely még fordítás alatt van ---


Az összetett szerves molekulák, mint az RNS-ben levő bázisok, nagyon törékenyek és instabilak, kivéve alacsony hőmérsékleteket. Nem maradnának együtt elég hosszú ideig, hogy az első önmásolódó elő-élet alapjaként szolgáljanak.

Forrás: Bergman, Jerry. 2000. Why abiogenesis is impossible. Creation Research Society Quarterly 36(4), http://www.creationresearch.org/crsq/articles/36/36_4/abiogenesis.html, Yahya, Harun. 2003. The secrets of DNA http://www.harunyahya.com/dna03.php



Lásd még: [1]


The source Bergman cites for the fragility of RNA bases (Levy and Miller 1998) disputes abiogenesis only at high temperatures, around 100 degrees Celsius. They also conclude, "At 0 degrees C, A, U, G, and T appear to be sufficiently stable (t1/2 greater than or equal to 106 yr) to be involved in a low-temperature origin of life." They also say that cytosine is unstable enough at 0 degrees Celsius (half life of 17,000 years) that it may not have been involved in the first genetic material. The discovery of a ribozyme without C-G bases shows that genetic material without cytosine is plausible (Reader and Joyce 2002).

If synthesis of nucleo-bases is catalyzed and hydrolysis is not, we expect the nucleo-bases to accumulate. Formamide, which can form under prebiotic conditions, has been found to catalyze the formation of nucleo-bases (Saladino et al. 2001; Saladino et al. 2003).

RNA degrades quickly today because there are enzymes (RNAses) to chew it up. Those enzymes would not have evolved if RNA degraded quickly on its own. If complex organic molecules were so fragile, life itself would be impossible. In fact, life exists even in boiling temperatures or at very high acidity.

Life need not have begun with highly stable molecules. Eigen and Schuster developed a notion of chemical hypercycles, in which many chemical components coexist; each component of the reaction leads to other components, which eventually reform the original one (Eigen and Schuster 1977). Chemicals involved in such a cycle need not persist longer than the duration of the hypercycle itself.

Organic molecules may have grown in association with stabilizing templates, such as clay templates (Ertem and Ferris 1996), or parts of the hypercycles mentioned above. References:

Eigen, M. and P. Schuster. 1977. The hypercycle. A principle of natural self-organization. Part A: Emergence of the hypercycle. Naturwissenschaften 64(11): 541-565. Ertem, G. and J. P. Ferris. 1996. Synthesis of RNA oligomers on heterogeneous templates. Nature 379: 238-240. Levy, Matthew and Stanley L. Miller. 1998. The stability of the RNA bases: Implications for the origin of life. Proceedings of the National Academy of Science USA 95: 7933-7938. Reader, J. S. and G. F. Joyce. 2002. A ribozyme composed of only two different nucleotides. Nature 420: 841-844. Saladino, R., C. Crestini, G. Costanzo, R. Negri and E. Di Mauro. 2001. A possible prebiotic synthesis of purine, adenine, cytosine, and 4(3H)-pyrimidinone from formamide: Implications for the origin of life. Bioorganic and Medicinal Chemistry 9(5): 1249-1253. Saladino, R., U. Ciambecchini, C. Crestini, G. Costanzo, R. Negri and E. Di Mauro. 2003. One-pot TiO2-catalyzed synthesis of nucleic bases and acyclonucleosides from formamide: Implications for the origin of life. ChemBioChem 4(6): 514-521.