Final answer:
A gene's physical location on a chromosome is known as its locus. Genes are the functional units of chromosomes and determine specific characteristics, while alleles are different versions of a gene that are always found in the same locus.
Step-by-step explanation:
A gene's physical location on a chromosome is known as its locus. The locus refers to the specific position on a chromosome where a gene is found. Genes are the functional units of chromosomes and determine specific characteristics, while alleles are different versions of a gene that are always found in the same locus. For example, in pea plants, the purple-flower allele (B) and the white-flower allele (b) are found at the same locus.