But in other parts of the world, and particularly for international itineraries involving multiple airlines, paper tickets are more common and it's taken 13 years from the time the first electronic ticket was issued in 1994 to the eradication of paper ticket stock issued by IATA.
The two DNA strands are held together by interchain hydrogen bonds. H-bonds pair the bases in one chain to the complementary bases in the other chain. (A/T and G/C). slide 2 of 4. Hydrogen Bonds in DNA A number factors are responsible for the stability of the DNA double helix structure, among them hydrogen bonds. Internal and external hydrogen bonds stabilize the DNA molecule. The two strands of DNA stay together by H bonds that occur between complementary nucleotide base pairs.
See Fig. 1. The nucleotides within each strand are held together by the phosphodiester bonds between the 5' carbon of one nucleotide and the 3 ' carbon of the adjacent nucleotdie. These strong covalent bonds form the the glue that holds the sugar/phosphate backbone together and thus act to keep each strand together.The two strands of DNA are held together by weak hydrogen bonds (remember, something must hold them together!) between the nitrogenous bases.The interesting (and very important) aspect of the Watson-Crick model is that these hydrogen bonds are base specific.he two strands of DNA are held together by weak hydrogen bonds (remember, something must hold them together!) between the nitrogenous bases. The interesting (and very important) aspect of the Watson-Crick model is that these hydrogen bonds are base specific.