How is an allele defined?

An allele is defined as different forms of a gene that occupy the same position on homologous chromosomes. This definition indicates that alleles represent variations of a specific gene that can result in different traits. For example, for the gene that determines flower color in a plant, one allele may code for red flowers while another might code for white flowers. This concept is crucial in understanding genetic variation and inheritance patterns in organisms.

The physical manifestation of a genetic trait pertains to phenotype, which is distinct from the concept of alleles that focuses on variations at the genetic level. The process of gene expression refers to how the instructions in our DNA are converted into a functional product, such as proteins, which is not what an allele is. Lastly, a variant of a chromosome refers to structural changes or mutations in chromosomes rather than the specific variations of a gene, or alleles, which are related to traits.