Using All the Atoms in the Universe
From the calculations in previous chapters, it could be guessed that to obtain a gene would be at least as difficult as to obtain a protein molecule. Instead of using all the atoms on earth, therefore, this time let us assume that
all the atoms of the entire cosmos have been made into sets of nucleotides, and that these are activated, ready for linkup. (Nucleotides are made of atoms of carbon, nitrogen, hydrogen, oxygen, and phosphorus.)
It will be presumed that each chain will polymerize or link up at the swiftest speed of atomic processes (of which the limit is said to be around 1016 per second as noted earlier).
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With each nucleotide being added at such a speed, the number of complete chains (genes) per second is 8.3 x 1012 in any one set. In a year, a set of nucleotides would produce 2.6 x 1020 genes, which we will round off to 1021.
Chance is trying for the first gene in the universe, so there is no pattern strand of DNA or RNA existing. The four different nucleotides will occur only in random order in the chain. If just one side of the ladder or double helix is obtained, it will be considered sufficient, in the thought that if one is obtained, the other side might form by base pairing.
<A name=ec10f12x> From standard estimates of the cosmic abundance of the elements,<A href="http://www.creationsafaris.com/epoi_c10.htm#ec10f11">
11 it can be found that phosphorus is the limiting element in forming activated nucleotides. There are estimated to be 1.5 x 1072 phosphorus atoms in the universe.
12 Three atoms of phosphorus are needed for each activated nucleotide. This will make 1068 sets, so that one copy of each of the four kinds of nucleotides is present at each point of the 1,200-unit chain being formed.
<A name=ec10f13x> If each set is producing 1021 sequences per year, that will be a total of 1089 different chains annually, using all of the appropriate atoms of the universe. As in the case of proteins, it is assumed that each chain will be dismantled immediately and another one built until there is a usable gene. This is done at the prodigious speed of eight trillion chains per second.
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The Number of Possible Orders in a Gene
There are three different ways to determine the number of possible sequences in a DNA chain. The general formula, it may be recalled, is: the number of kinds to the power of the number of units in the chain. If each order is equally likely, the probability of a particular sequence will then be one in the total of possible orders.
With four kinds of nucleotides, and a chain 1,200 long, the total of possible arrangements would be 41200, which is approximately 10722. The letters of a gene, however, are read in triplet codons (comprising sixty-four kinds of triplets) of which there are 400 in this size chain. If computed in this way, there would be a total of 64400 possible orders, and this turns out to be the same as when figured by individual letters, namely 10722.
<A name=ec10f15x><A name=ec10f16x> The reader may recall, however, that many of the twenty amino acids are coded by more than one triplet. The duplicate codons are thought by some to be “a historical accident,” Others believe they may be “perhaps a regulatory factor in some cases,”
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14 since nature is “seldom redundant” for very long.
15 As mentioned in the preceding chapter, evidence is accumulating that these seeming duplicates may serve the vital purpose of
regulating16 the synthesis of proteins. If that turns out to be true, then there would be no useless duplicates among the 64 codons,
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17 and the total real sequences would be the 10722 figure.