of authors. Some of them find it unacceptable (Miller, Orgel, 1974; Orgel,
1987) while others point out the advantages of RNA molecules in their
metabolism and reproduction due to catalytic and autocatalytic properties
(Pace, Marsh, 1985; Zaug, Cech, 1986; Cech, 1987) that have been
foreseen by Woese (1967, 1968), Crick (1968), Orgel (1968), Sulston, Orgel
(1971). This has given grounds to Alberts (1986), Lazcano (1986) and Gilbert
(1986) to assume that there has never existed a prebiotic translation
synthesis of proteins and their reproduction and metabolism have been
dependent on the catalytic abilities of RNA molecules. Gilbert has forwarded
the “RNA World” as a possibility.
On the basis of a large number of studies — the proving of the central
role of the different RNA molecules in protein biosynthesis (Crick, 1968,
and others) which has led to the postulation that this process can be carried
out in the absence of DNA but is impossible without RNA (Spirin, 1986), the
existence of biological replicative systems such as the ones in the viroids
(Diener, 1982) and viruses (Reanney, 1982) that are using single or twostranded RNA molecules, the enzyme reduction role of ribonucleotides in
the synthesis of the deoxyribonucleotides (Sprengel, Follmann, 1981;
Lammers, Follmann, 1983) — a large number of authors have
independently expressed their view that RNA has preceded DNA as
genetic material and has played a great role in the biological processes at
the early stages of cell evolution (Lazcano, 1986, 1998).
These facts have led to the alteration of the postulated Central
dogma in biology established after 1953 with the Watson and Crick model
of DNA — DNA → RNA → protein into DNA RNA → protein. A twoway arrow has been placed.
Despite the great achievements of biology the opinion of many authors
(Alberts et al., 1986; Oró et al., 1990 and others), which is shared by the
author of the book, is that it is still quite unclear how exactly protein
biosynthesis takes place. This is especially true for the initial stages of the
existence of living systems when they did not have at their disposal the
complex mechanisms of synthesis and reproduction that have emerged later
and have established themselves in the evolutionary process at the cell and
organism level. This problem will be treated again in Chapter 2, Section 2. 7
(Proteins).
Since by now there is no clear and convincing scheme about the ways
and mechanisms by which the abiotic formation of the monomers was
effectuated through the “lucky combination” of the atoms and their conversion
into polymers as well as there are no data about the exact timing of the
emergence of replication and translation in the biological systems, the problem
of the origin of life remains still unclear. Most justly Oró et al. (1990) conceive
the origins of replication and translation as “two major unsolved problems”.
According to the authors these mechanisms are of crucial importance to the