Every person is different and this is a product of nature (your DNA) and nurture (your environment). What's new and interesting about the DNA piece is both the availability of testing your DNA and the ability to optimize how bodies function based on the DNA. This is especially true with the MTHFR mutation and other mutations like this.
You may think that everyone makes biochemical molecules exactly the same but that is not true. The template is the same, but each person has slight alterations in the template (the DNA) creating differences in how biochemical molecules are produced and destroyed. These differences are partially what makes us unique. However, some of these alterations can also predispose people to certain health issues and MTHFR and food allergies are common examples of these.
What is DNA?
When diving into the complexities of MTHFR, understanding what DNA is helps paint a better picture of how genetic alterations occur across our population. Deoxyribonucleic Acid, or DNA, is made up of base pairs, like, as guanine, cytosine, and adenine thymine. The "double helix" of DNA is created by these base pair bonding together. Different combinations and sequences of these base pairs create the genetic code that tells our body which protein(s) to make and how to make them. When a change occurs in a base pair sequence from the normal, you get a different protein. That one change can cause a slightly different protein or a majorly different protein. It all depends on the spatial configuration of the molecule, but in any case, the change in base pairs will change the shape of the protein.