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.
Â· A tornado is a very violent windstorm. Â· 1  In a tornado the air is concentrated (pushed together). Â· 2  The air whirls upwards rapidly. Â· 3  A tornado is grey in colour and looks like an elephantâs trunk swaying down from the clouds to touch the ground with its tip. Â·  A tornado is only a tornado if it touches the ground.