Final answer:
The total of all alleles of a gene in a population primarily affects the allele frequency, which is central to population genetics and changes through natural selection.
Step-by-step explanation:
The total of all the alleles of a gene in a population affects the allele frequency. Allele frequency, also known as gene frequency, is the rate at which a specific allele appears within a population and is a fundamental concept in population genetics. It's the number of copies of one allele divided by all the copies of that gene in the population. When environmental factors favor an allele that confers an advantageous phenotype, that allele can become more widespread due to natural selection, altering the population's genetic makeup. Conversely, alleles that are disadvantageous may decrease in frequency or be eliminated from the population.