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.
Where the air for Tornado Alley comes from. 1  The warm moist air, called tropical maritime air, is swept up from the Gulf of Mexico and the Caribbean Sea due to lack of mountain barriers. During the spring months the Earth begins to warm, which adds to the layer of warm moist air which is close to the ground.