It has been known for years that organisms and populations adapt to environmental challenges by mutating DNA nucleotides that are particularly exposed during transcription. In other words, when faced with an environmental challenge a cell identifies certain genes which can help meet the challenge. But the gene might require some modification. And so when the DNA double helix is unwound (in order to make a copy of the gene) the exposed single stranded DNA is subject to mutation. Therefore mutations don’t occur randomly in the genome, but rather in the genes where they can help to address the challenge. But there is more. The gene’s single stranded DNA has certain coils and loops which expose only some of the gene’s nucleotides to mutation. So not only are certain genes targeted for mutation, but certain nucleotides within those genes are targeted in what is referred to as directed mutations. As one paper explained: Read more