For most character traits present in organisms, more than one allele exists. The different genes must have come about by chance alone, because we are dealing with genotype. The genotype of an organism includes both latent and patent genes. Only genes that have been activated are expressed in the phenotype. A new gene must first be expressed before natural selection comes into play.
As far as alleles are concerned, expression is governed by a complex system of dominance versus recessiveness. Furthermore, the frequency of genetic expression can also alter the phenotype. For example, the gene coding for growth hormone can influence the size of the organism. Variation in size does thus not necessarily require new genes, just differential expression of the same genes. An example of built-in variation in the gene pool can be seen in the differences between breeds of dogs. As to how the genes responsible for the variation came in to existence, chance or design are the only options given, since we are dealing with genotype.
By selecting from the built-in natural variation of the gene pool, various breeds of dogs and domestic cattle were produced. Great changes in physiology and morphology are involved, and evolution is here certainly excluded. Differences in dogs are greater than the differences in genera of the Canidae family.i
From a creationist perspective, the vast initial gene pool makes possible a vast range of adaptive morphologies and physiologies. This general gene pool is called "kind" in the Bible. Adaptive radiation as observed by evolutionists is thus nothing other than the end product of sorting the gene pool by outside factors, such as differences in climate and habitat. Gene patterns suited to the environment are selected and change is rapid.
Genetic expression is also influenced, so as to bring about differences in structural expression by the genes in terms of size. Differential hormonal modulation in response to environmental stimuli can alter the time and magnitude of response, effectively producing reproductively isolated communities which would be regarded as different species by evolutionists, but are in effect merely extremes of genetic expression within an existing gene pool. The vast numbers of latent genes would then be accounted for.
Evolutionists recognize that changes in genotype frequencies do occur to produce changes in gene distribution. They, however, explain most changes as resulting from chance mutations, and this is not tenable.
Even evolutionists admit that preadaptation must have played a major role in enabling organisms to survive environmental changes. Preadaptation, however, requires preexisting genes capable of responding to environmental stimuli—precisely what creationists claim. Where did these fully expressional genes come from? Once again, chance or design are the only options.
i R. K. Wayne, "Cranial morphology of domestic and wild canids: the influence of development on morphological change," Evolution 40 (1986): 243-261.