Class A (type D) CpG ODNs (CpG-A ODNs) contain a central palindromic phosphodiester (PO) CpG sequence and a PS-modified 3â poly-G tail. The poly G tails form intermolecular tetrads that result in high molecular weight ordered structures.
Why does a tornado form when cold and hot air meet? The collision of warm and cold air is not the direct cause of a tornado, nor is it absolutely necessary. When a cold air mass pushes into a warm air mass (this is called a câ¦old front) the warmer, less dense air is forced upwards.
The cold front lifts  the warm, moist air, sparking the development of thunderstorms. In  Tornado Alley a mass of dry air from the Rockies may also move in,  forming a dry line. This can also generate thunderstorms and can be  even more conducive for the formation of strong tornadoes than a  cold front.