The answer to what makes each person unique may lie in something called transcription factors. Your genes determine what you look like, but the way they bind to certain proteins may influence who you are.
Although your genes determine your appearance, the interaction between your gene sequences and key proteins can influence your physical and emotional development. A slight difference between genes can explain why one person likes ketchup on their eggs and another does not. Every person shares approximately 98 percent of their DNA, with a variation of only 0.025 percent between genes from one person to another.
In addition to this slight genetic difference, a person's uniqueness is affected by their personal experiences and their environment. Culture, beliefs, goals, habits and ethics all influence who you are as an individual. The opportunity for uniqueness exists in your physical, mental, emotional and spiritual makeup.