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.
When the temperature difference between the cold and warm air is large, thunderstorms and even tornadoes may form. The types of weather that are associated with a cold front are  thunderstorms that may become severe.After the front passes, the  temperatures become cooler and the weather becomes clear.ornadoes frequently form along cold fronts and dry lines.  Occasionally they may form along warm fronts. Some tornadoes form  from thunderstorms not associated with any fro â¦ nts.