The parasympathetic nervous system activates the relaxation, or rest-and-digest, response. Roughly the opposite of the fight-or-flight response of the sympathetic nervous system, the relaxation response involves restoration of energy reserves and other peace time functions, such as repair and reproduction.
On this day in 1953, Cambridge University scientists James D. Watson and Frances H.C. Crick announce that they have determined the double-helix structure of DNA, the molecule containing human genes.hough DNAâshort for deoxyribonucleic acidâwas discovered in 1869, its crucial role in determining genetic inheritance wasnât demonstrated until 1943. In the early 1950s, Watson and Crick were only two of many scientists working on figuring out the structure of DNA.
DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone. DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a personâs body has the same DNA.Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).he structure of the double helix is somewhat like a ladder, with the base pairs forming the ladderâs rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder. An important property of DNA is that it can replicate, or make copies of itself.