Which statement is accurate? a. a gene consists of two traits. b. an allele is one form of a gene. c. most alleles have many genes. d. an allele is made up of two genes.

B) An allele is one form of a gene.

A trait is usually determined by more than one gene, much less two traits, so A is false.
Alleles are a form of a gene, and any genes have usually two alleles, not the other way around, so C and D are both false.