Final answer:
A minor allele frequency can surpass 50% in a population due to genetic drift, natural selection, and population size, leading to fluctuations in allele frequencies and potentially resulting in a previously minor allele becoming predominant.
Step-by-step explanation:
A minor allele frequency can be >50% due to mechanisms such as genetic drift, natural selection, and population size effects. Genetic drift, which is more pronounced in small populations, is a change in allele frequency dictated by chance events rather than advantageous traits. Over time, allele frequencies can fluctuate and evolve as part of a random walk until one becomes fixed. Natural selection can rapidly increase the frequency of an allele if it confers a reproductive advantage, while alleles that decrease survival or reproduction can swiftly decline.
Pertaining to the idea that allele frequencies always add up to 100 percent, if a polymorphism exists where an allele's frequency becomes greater than that of the alternate allele, it is no longer the minor allele but becomes the major allele in the population. So, a minor allele frequency can exceed 50% when there's a shift in allele frequency due to the above-mentioned evolutionary forces.
For instance, in population genetics, the evolution of a population is marked by a change in allele frequencies, such as the case with the ABO blood type system. Several factors can influence these changes, and a sudden increase in one allele can lead to a scenario where what was once a minor allele becomes the predominant one.