Deoxyribonucleic acid, or DNA, is a polymer of nucleotides linked together by specific bonds known as phosphodiester bridges. The phosphate group (PO3) of one nucleotide links to the hydroxyl group (OH) of the following nucleotide.Hundreds of millions of these linkages occur within the DNA polymer.he two DNA strands are held together by interchain hydrogen bonds. H-bonds pair the bases in one chain to the complementary bases in the other chain. (A/T and G/C).
The master circadian pacemaker in mammals is located in the suprachiasmatic nucleus in the rostroventral hypotha-lamus (Figure 2). Lesion studies identified it in 1972, and in vitro and in vivo functional studies, as well as transplant studies, have repeatedly corroborated the finding since then.
A pacemaker is a device that administers electrical energy to the heart to stimulate contraction and regulate its rhythm. Pacemakers may be permanent or temporary (e.g. transcutaneous, transvenous or epicardial wires).The essential components of a pacemaker are: 1  Pulse generator (the power source).nd letter: Chamber sensed â dual chamber (atrial and ventricle). 3rd letter: Pacemaker response to a sensed event â dual response (can trigger or inhibit). Thus a pacemaker functioning in DDD mode can pace either or both the atria and ventricles.