| Next | Part 3 | Part 4 | Part 5 |

| Table of Contents for Evolution On Trial |

Mr. Tappin studied the papers in his hands for about five or ten seconds. When he had finished, he asked: "In the Chech and Zang study involving a particular kind of ribozymal activity, one comes across references to something known as "L-19 IVS RNA". What is this?"

"This is the working name," Dr. Yardley explained, "for a large molecule of ribosomal RNA. The L-19 portion of the designation refers to the 19 nucleotides that have been removed from an original sequence of 395 nucleotides by the catalytic self-splicing action of this molecule.

"Because the original sequence catalytically operates on, or intervenes with respect to, itself, it is referred to as an intervening sequence. This is the IVS component of the working name."

"What function is served when the 395 nucleotide polymer cuts off 19 nucleotides from itself?" the lawyer inquired.

"Apparently," replied the professor, "this provides a more accessible binding site on the L-19 IVS RNA molecule to which several other oligonucleotides, or short sequences of nucleic acid, can be brought together to form a bond through what is known as a transesterification reaction. In effect, the L-19 IVS RNA enhances the rate of hydrolysis that is characteristic of this sort of reaction by a factor of 10¹⁰, or 10 billion times.

"This kind of transesterification reaction has never been observed to occur between two free oligonucleotides. Consequently, the presence of a protein enzyme or, as in the present case, an RNA ribozyme is of paramount importance if such reactions are going to occur."

"How large," asked the lawyer, "is the binding site that is made available by the cleaving of the 19 nucleotides from the original 395 nucleotide IVS RNA molecule?"

"We believe it to be about 7 nucleotides, or so, in length," the professor answered.

"If the binding site is only 7 nucleotides in length," the defense counsel reasoned, "why is there a need for the other 388 nucleotides? Why doesn't the original IVS RNA molecule simply cleave off all but the 7 nucleotides that constitute the binding site?"

"First of all," pointed out the professor, "the 395 nucleotide sequence supervises the initial, precise process which eliminates the 19 nucleotides that render the binding site more accessible to the nucleotides which are to be chemically bonded together. Secondly, the remaining L-19 IVS nucleotide sequence also supervises, so to speak, the bringing together of nucleotides and, in doing so, is required to recognize three or more nucleotides in order to establish a reaction site.

"Consequently, the L-19 IVS RNA molecule has more base-sequence specificity for single-stranded RNA than many, if not most, protein enzymes that are involved in similar kinds of reactions under other cellular circumstances. In fact, this specificity may even rival the specificity of various DNA restriction endonuclease protein enzymes which key in on, and cleave, very specific bonds such as those occurring during the unwinding process of the double-helix structure which is preparing for replication.

"Various kinds of base-deletions studies have been done in relation to IVS RNA to determine just how much of the original 395 nucleotides are necessary for efficient cleavage-ligation activity. On the basis of these kinds of study, at least 300 nucleotides appear to be minimally required in order for efficient catalytic activity to be manifested."

"Does this mean," the defense counsel queried, "that all ribozymes would have to be this large in order to be effective catalysts?"

"At this point," the professor indicated, "we are not quite sure. There are molecules known as group-I introns whose core structure consists of about 100 nucleotides and which exhibit considerable catalytic activity.

"As a result, seemingly, not every ribozyme, necessarily has to be as big as, say, the 300 nucleotides which appear to be minimally necessary for effective IVS RNA functioning. There may be a range of possible ribozyme sizes depending on function and so on, but, at the present time, we do not know what the upper and lower limits of this range might be."

"Given the catalytic specificity of these ribozymes," postulated Mr. Tappin, "even if we were to select, say, a group-I intron consisting of 100 nucleotides, wouldn't the odds of generating this kind of specific sequence on a random basis be, at a minimum, 4¹⁰⁰, since there are four nucleic bases which could occupy any one of the 100 nucleotide positions in the entire sequence?"

"Yes, this is correct," the professor confirmed.

"Similarly, for the, let us say, 300 nucleotide IVS RNA molecule," the defense counsel added, "the odds of generating such a specific sequence on a purely random basis would be 4^300.. Is this right, Dr. Yardley?"

"Yes," said the professor.

"Previously, Dr. Yardley, you have suggested the entire Archean era was filled with mini-prebiotic laboratories. Let us suppose we were to give those laboratories about 400 million years to come up with the correct sequence for a ribozyme consisting of 100 nucleotides - the 400 million years being near the figure you cited in direct examination testimony for the length of time during which life is likely to have originated on Earth.

"Let us further suppose all activity in these mini-prebiotic laboratories stopped except work which was directed toward coming up with the right sequence for one specific ribozyme catalyst consisting of 100 nucleotides. How many experiments, Dr. Yardley, would have to be performed per day, over the course of the allotted 400 million years, in order to exhaust the 4¹⁰⁰ combinations of nucleotide sequences which are possible?"

The professor was silent for about 15 seconds and, then, said: "Probably, in the vicinity of 3 x 10⁸⁸ experiments per day."

"I've read somewhere, Professor," stated the lawyer, "I forget where, that the surface of the Earth covers about 196,938,800 million square miles. Assuming this figure to be correct and if we were to assume that every square mile of the Earth were to be dedicated to trying out experimental combinations of 100 nucleotides to come up with the specific sequence of our Group-I ribozyme, how many experiments would have to be performed per square mile in order to exhaust the possible combinations?"

"About 2 x 10⁹² experiments per square mile," replied the professor after a brief pause.

"Of course," Mr. Tappin indicated," we have been assuming in all of the foregoing that we are dealing with the same kind of nucleotides which occur in living organisms. If we add in the assortment of different pentose sugars, ribose forms, optical isomers, odd nucleic bases, and phosphate bonds that are likely to have been hanging around during Archean era times, then, Professor, won't we have to significantly revise all of the foregoing figures in an upward direction in order to factor in the increased possibilities for combining 100 nucleotides in a specific sequence?"

"Yes, we would," Dr. Yardley responded.

Mr. Tappin held up the papers in his hand. "Professor Yardley, according to the information available to me, an Escherichia coli, or E. coli, bacterium contains 4 million base pairs of nucleic acid. Let us assume, arbitrarily, that the first self-sustaining life form had only one-quarter as many base pairs - that is, 1 million base pairs. Would this be a fair assumption?"

"Nobody really knows," stipulated the professor. "No one knows how few ribozymes or enzymes one needs in order to have a self-sustaining, self-replicating organism or protocell.

"Obviously, one needs more genetic information than is carried by a virus since such entities presuppose the existence of a host's replicating capabilities in order to produce new generations of the virus. However, precisely how much more would be minimally necessary is, at the present time, an open theoretical question."

"Let's assume," the defense counsel proposed, "that the average ribozyme is 100 nucleotides in length. In an RNA-world scenario, how many ribozymes do you feel, Dr. Yardley, would be reasonably necessary to look after the catabolic and anabolic pathways of a minimally functioning protocell capable, I would presume, of, to varying degrees: self-replication, division, growth, membrane transport, ion pumping, energy storage, charge transfer, ribosomal activity and the like?"

"I only would be blindly guessing," the professor stated. "Maybe, somewhere between 100 and 200 ribozymal genes."

"Alright," Mr. Tappin suggested, "lets take the lower boundary figure of 100 ribozymal genes. This means, in effect, the mini-prebiotic laboratories would have to find a collective way of bringing together in one place and at one time, a specific sequence of 10,000 nucleotides, 100 times - which is 1 million base pairs - the number of base pairs we are assuming to have been in our pre-E. Coli life-form, divided by our arbitrary and average figure of 100 ribozyme genes.

"If we were to assume there were a naturally occurring pathway for synthesizing ribonucleic acids, and if we were to assume there were a plausible means of polymerizing these nucleotides under prebiotic conditions, and if we were to assume there were no cross-bonding of pentoses, odd nucleic bases, phosphates, optical isomers, or different forms of ribose, then there are 4^10,000 possible combinations for a series of sequences adding up to 10,000 polymerized nucleotides. Now, none of the foregoing takes into consideration the fact that even given such a specific sequence of nucleotides, the order in which the ribozymal genes are activated and deactivated, as well as when, or for how long, this process of turning the genes on and off takes place, all of this has to be factored into calculating a baseline probability figure.

"Consequently, the 4^10,000 figure is, very much, a lower boundary figure for calculating the odds of generating such an arrangement of nucleotides if one were to assume chance factors were to be the only determinate in inventing such an effectively, functioning system capable of self-replication. Would you agree with this, Dr. Yardley?"

"These are your figures, Mr. Tappin," indicated the professor, "but, for the sake of argument, I'm willing to work with them."

"Given the foregoing, Dr. Yardley, would you be surprised," asked the lawyer, "if I were to tell you there would have not been enough time, space, energy or organic materials on Earth for the mini-prebiotic laboratories to experimentally search through even an extremely minuscule fraction of the total possible combinations which rise from a protocell organism with a genetic repository of 10,000 nucleotides during the 400,000,000 year, or so, period in which life is thought to have originated according to evolutionary theory?"

"Look," the professor asserted, "sometimes one can get figures and numbers to dance to almost any tune one likes. There are many possibilities that are not being taken into consideration by your calculations."

| Next | Part 3 | Part 4 | Part 5 |

| Table of Contents for Evolution On Trial |