This selectivity is crucial for a large number of biochemical processes involving nucleic acids. Purity pairs, pyrimidine pairs, adenine-cytosine pair, or guanine-thymine pair are not normally formed. * Three hydrogen bonds between guanine (purine) and cytosine (pyrimidine). ![]() Note here that the top string goes from 5 to 3, left to right, while the bottom string goes from 5 to 3, right to left. * Two hydrogen bonds between adenine (purine) and thymine (pyrimidines) The bonds between the top string and the bottom string is called base-pairing where the term base refers to the nucleotides (because their pH is basic) and pairing refers to the hydrogen bonds. The selective pairing of adenine (A) with thymine (T) and guanine (G) with cytosine (C) is based on the number of hydrogen bonds established between one of the purine bases and the one of the pyrimidine bases: ![]() Therefore, two nucleic acid sequences are complementary when the nucleic bases of one can pair with the nucleic bases of the other in the opposite direction to form two paired antiparallel segments. ![]() In addition, two nucleic acid sequences can match only antiparallel, that is to say between segments of opposite directions. The pairings between nucleic bases, forming "Watson-Crick" base pairs, are, on the one hand, adenine with thymine, and, on the other hand, guanine with cytosine.
0 Comments
Leave a Reply. |