Molecules that make up the rails of the dna structure? ?

DNA has a "sugar-phosphate back bone", this means that the DNA "rails" are made up of deoxyribose (a sugar) and phosphates. Ribose is the sugar component of RNA, and all the other things on that list are DNA/RNA bases.  hope this helps :)

In the air and in the lower fre ah water

The principle of independent assortment describee how different genes independently separate from one another when reproductive cells develop.