What is it about DNA that determines one's traits?

The correct answer will be-genes.

Explanation:

The trait is the feature of an organism which can be quantified like the color of the flower while the phenotype is the variety of the color of the flower.

The trait and phenotype are controlled by the "genes" present on the DNA. The gene is that segment of DNA which contains code for the trait. The traits are controlled by the alleles present of these genes which when unite withe the homologous pair show its effect.

Thus, genes is the correct answer.