Which of the following is true about alleles?

Alleles are variations of a gene that can exist in different forms for a specific characteristic. Each gene typically has multiple alleles that contribute to the diversity of traits seen in organisms. For instance, a gene that determines flower color in a plant might have alleles for red, blue, or yellow petals, indicating that these different forms can influence the same characteristic—flower color.

The other statements do not accurately describe the nature of alleles. While they may control a single trait rather than multiple traits (which would imply a more complex genetic interaction), the notion that alleles are always dominant is incorrect, as alleles can be recessive, dominant, or codominant. Additionally, alleles are not always located on the same chromosome, as they can be found in different positions across various chromosomes in an organism's genome.