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.
Basic structure of DNA showing spiral backbone and different nucleotides (Forluvoft via Wikimedia Commons). DNA itself is made up of smaller molecules called nucleotides that link up together to form two chains that are twisted together, a bit like the separate strands of a rope.But this twisted chain is not physically used to make, or build anything else other than more molecules of DNA. flat layer of cells forms human skin and a layer of cells folded to form a tube is how things like intestines or windpipes are formed. Cells, not DNA, are what act as building blocks. So, starting with DNA and finishing with a human: Genes are made of DNA.