The Creation Explanation
|Life -- Miracle, Not Accident|
What is a gene mutation? It is the alteration in any way of the sequence of nucleotides in a gene in the long DNA molecule.16 This can result from the alteration of just one of the 18,000 to 54,000 atoms that make up the average gene. The types of mutations which have been observed include replacing one nucleotide with another one or with another kind of molecule, adding one or more nucleotides, or deleting one or more nucleotides. If such a mutation occurs, the coded message is changed, and the protein manufacturing system of the cell is ordered to produce a protein molecule which is different from the original design.
As a consequence the protein will function differently in the cell or may not function at all. The cell may function differently, poorly, or not at all. The tissues constructed of the mutated kind of cell may distorted or non-functional. The organism may be weakened in some way, die, or never achieve life. The mutation is correspondingly said to be either deleterious or lethal.
Gene mutations occur accidentally by natural processes in living organisms and can likewise be induced in the laboratory by the influence of chemicals or radiation. They are detected by their effect upon the bodily form or structure of plants and animals, upon their behavior, and upon their internal chemistry. In nature, mutations are relatively infrequent, but they do occur. What is their effect upon plants and animals? Have mutations been observed to improve the organisms, or are they normally deleterious or lethal?
In reply to these questions it can be affirmed that the vast majority of observable mutations are deleterious or lethal. It is now known that there are many mutations which affect the DNA only, because they involve the replacement of a genetic code letter with another code letter which only changes the codon to a "synonym" which codes for the same amino acid to be inserted in the protein molecule for which the original unmutated gene coded. These "synonymous mutations" are said to be "neutral," for they have no observable effect on the organism. It is said that they are not "expressed." In the case of expressed mutations, the mutant individual is in general either weaker than the wild variety or cannot live. Speaking of expressed mutations, Theodosius Dobzhansky, a renowned geneticist, stated that less than one percent of all mutations are favorable, and biologist Julian Huxley suggested a figure of only one out of a thousand. According to Dobzhansky, "Most mutants which arise in any organism are more or less disadvantageous to their possessors. The classical mutants obtained in Drosophila (fruit fly) show deterioration, breakdown, and disappearance of some organs." To be specific, some of the mutations observed in Drosophila include absence of eyes, change in size, shape and veining of wings, and changed eye color. In human beings, mutant genes cause several kinds of color blindness, defective enamel and other abnormalities of the teeth, hemophilia and many other inherited diseases, as well as other undesirable traits.
Evidence from horticulture reinforces the principle that mutants are normally weaker than the parent. Mutant rose varieties produced by neutron radiation, while possessing certain esthetically desirable traits, were always found to be less vigorous than the original stock. This is generally the case in both horticulture and animal husbandry. The stock is bred for traits which the breeder considers desirable, and a few of these traits result from gene mutations. Under human supervision on the farm, the new varieties are successful. However, allowed to breed wild, the plant or animal always tends to revert to the wild variety.
In nature some mutations cause their bearers to die out because they cannot reproduce themselves. The seedless orange is a mutant which man has learned to save and propagate by growing new seedless orange trees from cuttings. The grower cuts a small limb from a seedless orange tree and grafts it onto a regular orange tree. Without this help, however, the seedless Navel orange tree would have died out without reproducing itself.
Genetic research with bacteria has provided the greatest amount of data on mutations, because bacteria are easy to grow and to investigate, having a short generation time. Some forms are more viable under specific conditions--for example, in the presence of antibiotics. Bacterial strains resistant to antibiotics have made life difficult for the medical profession in recent decades. In such cases, however, it generally is not known whether the genetic factor or factors responsible for the resistance were already in the population or resulted from new mutations. In any event, there is always the tendency to revert to the wild strain in the absence of the special conditions which led to the development of resistance.
The often observed genetic degeneration of natural populations agrees with the biblical record of the divine curse which was imposed upon the entire creation as a consequence of Adam's sin. The original creation was perfect, and this perfection included the original gene pool of every created kind of organism. When the curse of Genesis 3 became effective, degenerative influences immediately began to affect every species. That the consequences have not been even more disastrous can be attributed both to the marvelous design of the mechanism of inheritance and to the gracious providence of God.
16. Watson, James D., (ref. 7), pp. 299-329; Curtis, Helena, (ref. 1), pp. 146-166; Moore, John N. and Harold S. Slusher, (ref. 1), pp. 441-461.