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Handedness: Left and Right 1
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Genetic material, DNA and RNA, is composed of nucleotides. In living things, nucleotides are always ??right-handed.? (They are called right-handed, because a beam of polarized light passing through them rotates like a right-handed screw.) Nucleotides rarely form outside life, but when they do, half are left-handed, and half are right-handed. If the first nucleotides formed by natural processes, they would have ??mixed-handedness? and therefore could not evolve life??s genetic material. In fact, ??mixed? genetic material cannot even copy itself (a).

Each type of amino acid, when found in nonliving material or when synthesized in the laboratory, comes in two chemically equivalent forms. Half are right-handed, and half are left-handed??mirror images of each other. However, amino acids in life, including plants, animals, bacteria, molds, and even viruses, are essentially all left-handed (b) ??except in some diseased or aging tissue (c). No known natural process can isolate either the left-handed or right-handed variety. The mathematical probability that chance processes could produce merely one tiny protein molecule with only left-handed amino acids is virtually zero (d).

A similar observation can be made for a special class of organic compounds called sugars. In living systems, sugars are all right-handed. Based on our present understanding, natural processes produce equal proportions of left-handed and right-handed sugars. Because sugars in living things are right-handed, random natural processes apparently did not produce life.

If any living thing took in (or ate) amino acids or sugars with the wrong handedness, the organism??s body could not process it. Such food would be useless, if not harmful. Because evolution favors slight variations that enhance survivability and reproduction, consider how advantageous a mutation might be that switched (or inverted) a plant??s handedness. ??Inverted? (or wrong-handed) trees would proliferate rapidly, because they would no longer provide nourishment to bacteria, mold, or termites. ??Inverted? forests would fill the continents. Other ??inverted? plants and animals would also benefit and would overwhelm the balance of nature. Why do we not see such species with right-handed amino acids and left-handed sugars? Similarly, why are there not more poisonous plants? Why don??t beneficial mutations let most carriers defeat their predators? Beneficial mutations are rarer than most evolutionists believe.

(a). ??Equally disappointing, we can induce copying of the original template only when we run our experiments with nucleotides having a right-handed configuration. All nucleotides synthesized biologically today are righthanded. Yet on the primitive earth, equal numbers of right- and left-handed nucleotides would have been present. When we put equal numbers of both kinds of nucleotides in our reaction mixtures, copying was inhibited.? Leslie E. Orgel, ??The Origin of Life on the Earth,? Scientific American, Vol. 271, October 1994, p. 82.

??There is no explanation why cells use L [left-handed] amino acids to synthesize their proteins but D [right-handed] ribose or D-deoxyribose to synthesize their nucleotides or nucleic acids. In particular, the incorporation of even a single L-ribose or L-deoxyribose residue into a nucleic acid, if it should ever occur in the course of cellular syntheses, could seriously interfere with vital structure-function relationships. The well-known double helical DNA structure does not allow the presence of L-deoxyribose; the replication and transcription mechanisms generally require that any wrong sugar such as L-deoxyribose has to be eliminated, that is, the optical purity of the D-sugars units has to be 100%.? Dose, p. 352.

(b). An important exception occurs in a component in cell membranes of eubacteria. There the amino acids are right-handed. This has led many to conclude that they must have evolved separately from all other bacteria. Because evolving the first living cell is so improbable, having it happen twice, in effect, compounds the improbability. [See Adrian Barnett, ??The Second Coming: Did Life Evolve on Earth More Than Once?? New Scientist, Vol. 157, No. 2121, 14 February 1998, p. 19.]

(c). Recent discoveries have found that some amino acids, most notably aspartic acid, flip (at certain locations in certain proteins) from the normal left-handed form to the right-handed form. Flipping increases with age and correlates with disease, such as Alzheimer??s disease, cataracts, and arteriosclerosis. As one ages, flipping even accumulates in facial skin, but not other skin. [See Noriko Fujii, ??D-Amino Acid in Elderly Tissues,? Biological and Pharmaceutical Bulletin, Vol. 28, September 2005, pp. 1585??1589.]

If life evolved, why did this destructive tendency to flip not destroy cells long before complete organisms evolved?

In the Beginning: Compelling Evidence for Creation and the Flood - 35. Handedness: Left and Right