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.
1 Winds pushing disparate air masses converge in tornado alley. 2  Colliding air, known as fronts, have nowhere to go, therefore they rise. 3  Tropical air, when forced upward, encounters naturally cooler air (hence, snow-topped mountains). 4  Like a hot air balloon, the warm air rises freely.