“When examining evidence relevant to a given belief, people are inclined to see what they expect to see, and conclude what they expect to conclude. Information that is consistent with our pre-existing beliefs is often accepted at face value, whereas evidence that contradicts them is critically scrutinized and discounted. Our beliefs may thus be less responsive than they should to the implications of new information”---Thomas Gilovich
All cells can be categorized as either prokaryotes (bacteria) or eukaryotes. Both utilize ATP (adenosine tri-phosphate) as a universal source of energy. ATP generation is called "respiration." Complex multicellular plants and animals are composed exclusively of eukaryotic cells, but almost all DNA knowledge is based on prokaryote research. The differences between these two types of cells are so great as to negate the relevance of present DNA knowledge to medicine.
Prokaryotes (bacteria) respire (generate ATP) via their cell wall. As a consequence they are limited to individual existence, small size, and a few shapes such as spheres and rods that optimize their surface area relative to their contents. They can communicate with one another, coordinate their activities, and exchange genetic information, but they cannot sub-specialize or form complex multicellular structures. They contain no internal structures visible by a microscope. Their DNA floats free in their cytoplasm. They "transcribe" their DNA genetic information to RNA molecules that "translate" the information into proteins and enzymes that enable cellular functions.
Eukaryotes are vastly more capable and complex than prokaryotes. They exist both as independent free-living cells and as complex multicellular plants and animals. Their cytoplasm contains "organelles" that perform specific functions. These include mitochondria, chloroplasts, endoplasmic reticulum, vacuoles, Golgi apparatus and the nucleus. The mitochondria utilize oxygen and glucose to generate ATP within the cell via the Krebs Cycle, which enables eukaryotes to grow much larger than prokaryotes, differentiate into specialized cells, engage in chemotaxis (movement toward a source), and form complex multicellular plants and animals. Their mitochondria and chloroplasts contain independent DNA that replicates in the cytoplasm, but the nuclear DNA that governs embryological development is confined within the the thick nuclear membrane.
Nuclear DNA does not utilize the transcription/translation mechanism, and the means by which it communicates outside the nucleus, let alone outside the cell, remains unknown (see "The Central Dogma of Molecular Biology"). Stress theory postulates that chromosomal DNA controls PAR (protease activated receptors) on the cell surface via a mechanism that has yet to be identified to enable cell specialization and differentiation during embryological development, tissue repair, and malignancy.