Triggers of nonallergic rhinitis symptoms vary and can include certain odors or irritants in the air, changes in the weather, some medications, certain foods, and chronic health conditions. A diagnosis of nonallergic rhinitis is made after an allergic cause is ruled out.
DNA extraction. For the various methods, see Nucleic acid methods. DNA isolation is a process of purification of DNA from sample using a combination of physical and chemical methods. The first isolation of DNA was done in 1869 by Friedrich Miescher. Currently it is a routine procedure in molecular biology or forensic analyses.
DNA helicase is an enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between the complementary bases. It's easy to remember the name because it has part of the word helix in it. You can imagine it sort of as a wedge that forces apart the two strands, just like the slider on a zipper wedges apart the two long rows of teeth.