At the chemical level, the DNA of prokaryotic cells, which have no nuclear membranes, and that of eukaryotic cells, which have separate, membrane-enclosed nuclei, is identical. DNA is a long, double-stranded molecule containing a backbone of repeating, alternating sugar and phosphate units.
Simple cuboidal epithelium is a type of epithelial tissue found in the body. It is a single layer thick and made of cube-shaped cells. This type of tissue is found lining parts of the body such as the kidney tubules and walls of respiratory bronchioles.
Simple columnar epithelium consists of a single layer of tall (columnar cells). Simple columnar epithelium is usually involved in active secretion and/or absorption of material across the single cell layer, or (if ciliated) in movement along the surface. By convention, a stratified epithelium is described according to the shape of cells on its free surface. 2  Regardless of whether the surface cells are squamous, cuboidal, or columnar, the underlying cells are usually cuboidal.