The previous thread on this subject didn’t end with much agreement. However, I took my time to revisit the literature on genomes, and it was pretty obvious I had some things wrong.
Is DNA a blueprint? Yes. Blueprint for what? Building proteins and RNA. That’s it. So where do we get information to build new cells? That information lies within the (parent) cell, not just in DNA.
Don’t get me wrong. All the proteins and RNA a cell will ever make is encoded in DNA (or whatever the organism’s genome is), and it is these proteins and RNA that build cells. However, there are over 200 cell types in the human body, but each has exactly the same DNA sequence. To make a liver cell, certain segments of DNA need to expressed, while others are repressed and this has to be accurately timed. This applies to every other cell type as well.
Thus, its pretty clear that DNA encodes everything it takes to give a liver or heart cell. So while it is a blueprint (construction plan) for making proteins and RNA, it doesn’t play that role for cellular differentiation. Instead, DNA is recipe book or catalog of plans for making a wide variety of cells. The blueprint for building a cell lies within the cell itself, and is inherited from parent cells. The information needed to make a liver cell lies in DNA, specific receptors, enzymes, transcription factors, etcetera. That information present in all these cellular constituents is the blueprint.
For a review on genome, see this article: