DNA twists because of the 3 dimensional structure of the linking molecules along its backbone. These are phosphate molecules and 2-deoxy-D-ribose molecules. The base pairs link to this backbone using covalent bonds but link in the centre using hydrogen bonds. This linking holds the strand in place and supports this twist from both sides. RNA also twists but uses D-ribose instead meaning the twist will be a little different. The links are made from two Purines (double-ringed structures Adenine and Guanine) that attach to Pyrimidines (single-ringed structures Thymine and Cytosine). NOTE: DNA does not have to be double stranded, single stranded DNA is found in the viruses. RNA is usually single stranded but can also be double stranded. The four possibilities are one of the ways various virus families are classified. Try searching DNA in Wikipedia. More There are ten links to the turn (twist) because of the pentagonal symetry of phosphorus in the linking phosphate molecules
The 4 nucleotides in DNA are paired up to where Adenine is always across from Thymine, and Cytosine is always across from Guanine on the double helix.
There are a lot of variables including climate, temperature, air supply, humidity and air movement. I've had mold appear in a coffee cup over night in humid areas open to the outside. Northern areas with lower temperatures are less likely then hot and humid areas in the south.
Haustration is the mixing of feces to expose it to the surface of intestine to absorb water.
they are sac like structures foldings in large intestine. At each of these constrictions, about 2.5 centimeters of the circular muscle contracts, sometimes constricting the lumen of the colon almost to occlusion. At the same time, the longitudinal muscle of the
colon, which is aggregated into three longitudinal strips called the teniae coli, contracts. These combined contractions of the circular and longitudinal strips of
muscle cause the unstimulated portion of the large intestine to bulge outward into baglike sacs called haustrations.