You’re 99.9% genetically similar to every other person in the world. Let me explain: each cell has a nucleus, inside of which float a number of chromosomes. A few exceptions aside, all your cells have 46 chromosomes in each nucleus, 23 from your father and 23 from your mother. Each chromosome is made up of deoxyribonucleic acid, or DNA, which is responsible for the creation of protein, the key ingredient to life.

As you can see in above picture, DNA consists of only four basic components, called nucleotides: adenine (A), thymine (T), guanine (G) and cytosine (C). The order in which these nucleotides occur constitutes the human genome. As far as we know today, only 3% of all combinations of DNA (genes) constitute a useful function in our body. The other 97% seems to have no particular function and is called non-coding DNA.

DNA replicates by splitting in half along the length of the spiral helix and connecting with a different half. Adenine can only connect with thymine and guanine can only connect with cytosine. This makes DNA replication a fairly simple and perhaps even boring process, but one that is incredibly accurate. However, the interesting part is when the process is not accurate, i.e. when a nucleotide arrives in the wrong place.

Biochemists call this wrongly placed nucleotide connection a single nucleotide polymorphism, or snip. Most of the time, snips happen in non-coding DNA and will not make a difference. But every once in a while, a snip occurs in an important gene, which would leave the person in question with either a peculiar advantage, such as protective pigmentation, or a disadvantage, such as a predisposition to a particular disease. It’s exactly these snips that account for the 0.1% difference between you and every other person.

Your snips will most likely be in a different place than any other person’s. That means there is no such thing as a single human genome. If we look at a certain strand of DNA in a particular place, it is highly likely at least one person in the world will not have the same DNA there, but will have a snip instead. So although we are 99.9% genetically the same, each individual is also very different from any other person. Together we are unique. Truth again is found in a dichotomy.