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.
Transitional epithelium is a stratified epithelium in which the shape of the surface cells changes (undergoes transitions) depending on the degree of stretch.When a transitional epithelium is not stretched (for example in an empty bladder) the cells of the surface layers are large and rounded.Arrows labeled c indicate several large rounded cells which have been outlined on the photo.hen a transitional epithelium is stretched (as it would be in a full bladder) the cells of the surface layers are pulled into a flatter shape. Unlabeled arrows indicate base of the epithelium. ct = connective tissue. lu = lumen.