Final answer:
Genetic mutations are quite common due to the number of genes in an organism's genome, and while many are harmful or neutral, some are beneficial and drive evolutionary change. Mutations, including harmful ones like those causing sickle-cell anemia, can persist if they confer survival advantages under certain conditions.
Step-by-step explanation:
Genetic mutations can be described as changes in the DNA sequence, and they are a natural part of the genetic process. While individual mutations are relatively rare with a probability between 1 in 10,000 and 1 in 100,000 for a given gene, the sheer number of genes in an organism's genome means that each individual is likely to have multiple mutations. Therefore, genetic mutations are quite common when considering the totality of an individual's genetic material. Not all mutations are harmful; there's a variety of effects. Some are deleterious, causing diseases like cystic fibrosis or cancer, but occasionally a beneficial mutation occurs, which can help an organism adapt — like the CCR5 mutation providing resistance to HIV.
When considering the overall impact of mutations, the majority are neutral or harmful, but the rare beneficial mutations are a driving force behind evolutionary change. For example, despite the sickle-cell gene being associated with negative health outcomes, it persists in certain populations because it provides a survival advantage against malaria.