I think what most people misunderstand is the roll DNA plays regulating cell function ... all the myriads of proteins that have to be synthesized in the cell is mind-boggling ... and every single one of these proteins have to be transcribed from the cell's DNA ... we know how that process works right down to the molecular level ... more strands of DNA performing these function, the less stress on any single DNA strand ...
It's worth studying Sox9.
It has an L-shaped region that sits in the DNA, but it doesn't do much of anything until a partner protein binds next to it. Depending on the partner, the gene it attaches to can be either upregulated or downregulated.
So look what this means - lots of our genes have a "Sox9 binding sequence" - it's the same sequence over and over again, that matches the shape of the protein. But the action depends on the sequence right next to it, which is where the partner binds.
For a detailed example, see chondrocytes. These are the cells responsible for cartilage formation. (During development these all derive from stem cells). Chondrocytes come from mesenchyme, and develop into skeletal components.
There is a fairly common Sox-9 mutation that leads to campomelic dysplasia, which if the victims survive to adulthood looks kind of like this:
But the kids are fucked up, their bones don't grow right because the cartilage doesn't grow right. Here are some examples:
insight.jci.org
Sox-9 is in a lot of different cells, and it functions differently in each one. It's definitely involved in tissue regeneration. To find out which cells use it, there is an antibody that visualizes it.
The SOX9 AB5535 antibody is a laboratory reagent used to detect the presence and quantify the levels of the SOX9 protein in biological samples. SOX9 is a transcription factor that plays a crucial role in the regulation of various cellular processes, including chondrogenesis, sex determination...
www.pubcompare.ai
This antibody was originally cloned from live rabbits, in other words it started in the wild, as an auto-immune disorder.
Sox-9 undergoes post-transcriptional modification. It gets methylated, and it gets phosphorylated by a kinase. Both of these determine what it binds with.
Sox-9 interacts with a whole ton of membrane proteins, and malregulation is involved in various cancers. For example -
It binds with different cofactors at different times in development.
This is what it looks like during sex determination:
Over 4 billion years of evolution there's a whole ton of molecules that bind to each other and affect each other. Each one of them is regulated by a dynamic, could be negative feedback or positive feedback or both in various combinations. If one molecule changes shape it'll affect the function of half a dozen others. What makes a stable species is the ability of particular combinations to work together.
Sox-9 is a great case study because it's a chameleon, it's involved in just about every cell but it has a different function in each and different dynamics and timing, depending on which other molecules are involved. Sometimes it upregulates itself, it guarantees its own presence. Other times it downregulates and goes away, which alters the downstream behavior of dozens of other genes and proteins.
Sox-9 is involved in "sex reversal", where an XY reverts to female. There's a whole ton of current research about how it relates to SRY. All this kind of stuff is showing us how development really works.
