If it is a long run, 16 gauge is preferred. If the run is very short, you probably can use 18 gauge with no apparent difference in sound. But the cost difference is fairly small, so 16 gauge is preferred. There is no shielding on speaker wire, so the covering is of little import.
The backbone of the DNA strand is made from alternating phosphate and sugar residues. The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings.
These strands of DNA are made of nucleic bases (adenine, thymine, cytosine, and guanine), phosphates, and sugars. These components form DNA into the double helix shape we associate with DNA (the twisted ladder shape.) The nucleic bases are held together in the middle of the two strands by weak hydrogen bonds. This is what we know contemporarily as a strand of DNA. Strands upon strands of DNA are then packaged together (with protein formations generally called histones) to form what we know as the chromosome.