What is the gene pool in population genetics?

• A. The collection of genes present in a single organism.
• B. The measure of gene expression in a population.
• C. The total sum of all alleles and their frequencies in a population.
• D. The set of genes used during reproduction.

Answer: (C)

In population genetics, the gene pool is the total collection of alleles present in all individuals of a population and the frequencies with which those alleles occur. It’s the reservoir of genetic variation that can be passed to the next generation, and it can change over time as mutation, natural selection, genetic drift, migration, and recombination alter how common each allele is. For a locus with two alleles, A and a, if their frequencies are p and q (with p + q = 1), the gene pool is described by those values, and any shift in p or q means the population’s genetic makeup is changing. This concept helps explain evolution: even if the same alleles remain, their relative frequencies can move, reshaping traits in future generations. The other options don’t fit because a single organism’s gene collection is its genome, not the population’s, gene expression measures how much a gene is turned on rather than which alleles exist, and the set of genes used during reproduction doesn’t capture the full allelic variation across the population.