I was reading the article “Introduction to Evolutionary Biology” Version 2 by Chris Colby (on the talkorigins website) and came across the following sections -: Except in rare cases of high gene flow, new alleles enter the gene pool as a single copy. Most new alleles added to the gene pool are lost almost immediately due to drift or selection; only a small percent ever reach a high frequency in the population. Even most moderately beneficial alleles are lost due to drift when they appear. But, a mutation can reappear numerous times. … J. B. S. Haldane developed many of the mathematical models of natural and artificial selection. He showed that selection and mutation could oppose each other, that deleterious mutations could remain in a population due to recurrent mutation. Does this mean that a section of DNA will mutate in a certain way. But if that mutated section of DNA is not taken up in the species offspring then it is likely that more sections of DNA will be mutated in exactly the same way giving the new genetic sequence a better chance of passing into the next generation?