Answer:
A homologous pair
Step-by-step explanation:
In determining the expression trait of humans, this is based on the homologous chromosomes. This in turn comprised of alleles otherwise known as homologous alleles. The homologous loci are thereby located in these alleles which served as the formation of traits when combined.
Hence, normally, A HOMOLOGOUS PAIR is required to determine the outward expression of a trait?