Which type of allele occurs most frequently in nature?

The concept of "normal allele" refers to variants of genes that produce traits commonly found in a given population. Normal alleles are generally those that are most adapted to the environment in which a population exists and are often those which have been selected for over generations through natural selection. These alleles typically confer traits that are beneficial for survival and reproduction, making them more likely to be passed on to subsequent generations.

In contrast, recessive alleles may not manifest unless present in a homozygous condition, which can limit their frequency in the population if they confer disadvantageous traits when expressed. Dominant alleles can also be common, but they do not encompass all frequently occurring variants in a population, as some dominant traits may not represent the majority of the genetic variation. Mutant alleles, by their nature, are less common than normal alleles since they arise from rare changes in the genetic material.

Therefore, the term "normal allele" encompasses those alleles that are prevalent and well-adapted to the existing conditions of the environment, aligning with the idea that they occur most frequently in natural populations.