Correct Option: 1
Step 1: Define gene pool.
The gene pool encompasses the complete genetic material, including all alleles for every locus, present within a population or species. It signifies the range of heritable genetic variations.
Step 2: Clarify related terms.
Genetic drift: Denotes chance alterations in allele frequencies within a population.
Gene frequency: Represents the proportion of a particular allele within the gene pool.
Gene mutation: Refers to an enduring alteration in a gene's DNA sequence. \[ \therefore \text{The correct answer is: Gene pool.} \]