The two alleles of a gene pair are located on -

Homologous Chromosomes

The correct answer is Option (3) → Homologous Chromosomes 

Homologous chromosomes are pairs of chromosomes that are similar in shape, size, and genetic content (one inherited from each parent).Each gene occupies a specific locus (position) on a chromosome, and the two alleles (alternative forms of the gene) are found at the same locus on each homologous chromosome