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.
On a single strand of DNA the nucleotides are held together by covalent bonding between the phosphate group bonded to the 5' end of the deoxyribose, which bonds to another deo â¦ xyribose molecule attached to the next nucleotide on the strand at the 3' end of the sugar. This is what holds together a single strand. When two strands of DNA that have exactly complementary base pairing (Adenine bonds with only Thymine, and Cytosine with Guanine) the base forms a hydrogen bond to the base on the opposite strand, only if the base pairing is complementary.