Which of the following best defines genetic drift?

• A. A selection process driven by environmental pressures
• B. A random change in allele frequencies
• C. A mechanism of natural selection
• D. A process that eliminates weak alleles

Answer: (B)

Genetic drift is best defined as a random change in allele frequencies within a population. It is a mechanism of evolution that occurs due to chance events rather than through natural selection. As populations grow or change over time, particularly in small populations, certain alleles may increase or decrease in frequency simply due to random sampling of organisms. This randomness means that some alleles may be lost entirely, while others may become more prevalent, leading to evolutionary changes that are not necessarily advantageous or driven by environmental pressures.

In contrast to processes like natural selection, which favor alleles that provide a survival or reproductive advantage, genetic drift does not involve adaptive mechanisms. It can lead to significant changes in genetic diversity and population structure, especially in isolated populations, where the impacts of random events can be magnified. Because it operates independently of the fitness of the alleles involved, genetic drift can significantly shape the genetic landscape of a population over time.