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.
Cutting and Splicing DNA Molecules. If you want to insert a piece of new DNA (foreign DNA) into an existing strand you'd have to cut the existing strand, somehow position the foreign DNA, and then join the strands. This joining is called ligation and can be done with the enzyme DNA ligase. Restriction enzymes are produced by bacteria and function to protect bacteria from foreign DNA (like viruses). Restriction enzymes work by degrading foreign DNA. Restriction enzymes recognize and cut the sugar phosphate backbone of the DNA molecule at specific sites on a strand of DNA. The restriction enzyme recognition site is determined by a specific sequence of nucleotides. Thousands of restriction enzymes have been isolated, although many share the same recognition sequence.