First off, thank you for your reply robertling. Your reply has sparked some more questions. I realize this might be a totally inane discussion so thanks again.
If you were to implant a gene in a pre-existing plant, you'd have to implant them into the meristematic tissue (which are the progenitor cells). A meristem is the tissue in most plants consisting of undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place.
A. Then theoretically in the meristem part of a branch on an apple tree, you could implant a modified DNA sequence to say "grow apricots instead of apples" and that branch would continue to grow and then produce apricots?
B. Also, if this is the case, would the act itself of implanting new DNA be an interruption of the life process in any sense? Would life be ''on hold'' for a split second while the new DNA was recognized by the progenitor cells? (Sort of a weird question but has spooky metaphysical implications "In Medias Res")
No... This wouldn't work, unless you were to insert the gene into the progenitor cells. The most common progenitor cells in a human are the cells found in the bone marrow, that make new blood every day.
Ok, so I'm wrapping my mind around this. Wikipedia says "A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell. Progenitor cells are found in adult organisms and they act as a repair system for the body. They replenish special cells, but also maintain the blood, skin and intestinal tissues."
C. I don't quite grasp the cause & effect here. What's pushing a progenitor cell to differentiate? What determines its "target" cell? I understand that DNA will determine what the target cell will be, but does this also mean that DNA is responsible for guiding cell differentiation?
Once a cell is damaged, it programs itself to die either internally or by presenting the foreign object inside of it to immune cells, which in turn release enzymes to digest and kill it.
D. Hmm. I once read that the cells composing our bodies all die and are replaced cumulatively over 7 years. If there was sufficiently advanced technology to scan and identify cells on the verge of death or that have just died, would it be possible to catch the progenitor cell on its way to replace the dead one and inject it with new DNA thru nanotechnology, etc. that still maintains the 'life-integrity' of the differentiated tissue it is going to?
E. How much of the activation of DNA sequences or "turning on" of genes is circumstantial and environmentally conditioned?
F. Here's a far out hypothetical situation, I'm sure there's no research out there at all, so an educated guess is surely welcome: Let's say you had your skin removed or slowly replaced with a photosynthetic membrane of sorts that possessed all of the same structural requirements of skin but allowed you to derive enough energy from the sun to live. What would happen? Let's say all you had to do was take a multivitamin to sustain the nutrients like iron required of your body as well. On a technical level, would the photosynthetic sugar diffuse through your skin cells into your blood stream and be carried to wherever it needed to go? would your stomach and digestive tracts become damaged from inactivity? My gut feeling tells me there'd be a horrible implication in the long term, but I don't know scientifically whether it's the case or not. Again, any speculations based on science are welcome.
Thank you again!
-Kurtron