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.
The body clock, or circadian clock, is an internal clock that keeps track of time. Circadian comes from circa-diem meaning around a day. So in a mouse for example it is about 23.5 hours and for a human its about 24.5 hours. If you are kept in constant darkness your body will still work to around a 24-hour cycle. It is not just being driven by light and dark. It is an intracellular clock so if you look in individual cells they are all able to keep time as well. If you put cells in a dish they will show 24-hour changes in gene expression.