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.
How are nucleotides held together vs how DNA strands in a DNA molecule are held together? The nucleotides are linked together covalently by phosphodiester bonds through the 3'-OH group of one sugar and the 5'-PO3 of the next, into polynucleotide chains. A DNA molecule is composed of two of these polynucleotide chains (DNA strands) which are held together by hydrogen bonds between the paired bases. DNA is wound into a _______ _______.