1. As the Bible hints at (as a man thinks in his heart, so is he--as well as Scriptures about what we say etc) research has demonstrated that what we THINK about a LOT and/or what we SAY a lot--changes even our DNA. I don't know in what ways but they are more or less lasting changes.
2. There are ... what's the word ... epigenetic ??? changes. i.e. the expression of this or that gene or set of genes CAN BE AND ROUTINELY IS changed by the internal/external environmental experiences, conditions.
Maybe some micro-biologists by profession will chime in on this topic.
I just finished reading a book by Dr. Leaf “Switch on Your Brain” and she talks about epigenetics. It is amazing about how you can change your life due to your words.
The DNA in every cell?
The resulting organism, a human being, has more complexities as it adjusts to the environment it exits in. But there is a limit to how much oinformation can be coded into a sequence of data that is 3 billion units in length.