Context: Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotype traits. Colloquial usage of the term "having a gene" (e.g., "good genes," "hair colour gene") typically refers to having a different allele of the gene. Genes evolve due to natural selection or survival of the fittest of the alleles.

Question: What do mutations in a gene sequence lead to?
Answer: different variants, known as alleles

Question: What do alleles do?
Answer: encode slightly different versions of a protein

Question: What do alleles cause?
Answer: different phenotype traits

Question: What does "having a gene" or a "good gene" typically refer to?
Answer: having a different allele of the gene

Question: What causes genes to evolve?
Answer: natural selection or survival of the fittest of the alleles