Final answer:
Sewall Wright demonstrated that the probability an allele will drift to fixation in a population is equal to that allele's initial frequency. This process, known as genetic drift, is a random fluctuation of allele frequencies and is most significant in small populations. Option 1 is the correct answer.
Step-by-step explanation:
Sewall Wright contributed significantly to our understanding of population genetics and evolutionary biology. He proposed the concept known as genetic drift, which is the change in the frequency of an allele in a population due to random sampling of organisms. The question at hand concerns the probability that any given allele in a population will become fixed, meaning it will be the only allele present in the population for a particular gene.
According to Wright's principles, the probability that a specific allele will drift to fixation in a population is equal to that allele's initial frequency. Therefore, if an allele starts off being present 50% of the time in the gene pool, it has a 50% chance of eventually becoming fixed. However, it is essential to acknowledge that this process is entirely driven by chance and will vary greatly, especially in small populations.
To illustrate, imagine a scenario where a population has two alleles, A and B, with initial frequencies of 0.6 and 0.4 respectively. Over time, as generations pass, these frequencies will fluctuate due to random events affecting survival and reproduction until one allele becomes fixed. This random walk of allele frequencies is more pronounced in smaller populations, where even the loss or gain of a few individuals can have a significant impact on the genetic composition of the entire population.
It's important to note that this process differs from natural selection, where allele frequencies change in a directionally non-random manner due to differential survival and reproduction of individuals carrying certain alleles. Genetic drift is a mechanism of evolution that operates alongside natural selection, mutation, and gene flow, shaping the genetic diversity within populations.
The correct answer to the question is option 1, meaning the probability that any given allele in a population will drift to fixation is equal to the allele's initial frequency.