Here's why:
* DNA contains the genetic blueprint: DNA holds the instructions for building and maintaining your body.
* Cells need instructions: Every cell needs to know how to function and replicate.
* Exceptions: The only cells in your body that don't have DNA are red blood cells. They lose their nuclei (where the DNA is stored) during development to make room for more oxygen-carrying hemoglobin.
So, almost every cell in your body has a copy of your DNA, ensuring that your cells can function and replicate correctly.