What purines and pyrimidines basically are??
What are Purines and Pyrimidines?: The Basics Each DNA strand has a ‘backbone’ that is made up of a sugar-phosphate chain. Attached to each one of these sugars is a nitrogenous base that is composed of carbon and nitrogen rings. The number of rings this base has determines whether the base is a purine (two rings) or a pyrimidine (one ring). The purines on one strand of DNA form hydrogen bonds with the corresponding pyrimidines on the opposite strand of DNA , and vice versa, to hold the two strands together. Within DNA molecules, this is their most important function and is known as base pairing. Because hydrogen bonds are not as strong as covalent bonds, base pairings can easily be separated, allowing for replication and transcription.
Because purines always bind with pyrimidines – known as complementary pairing – the ratio of the two will always be constant within a DNA molecule. In other words, one strand of DNA will always be an exact complement of the other as far as purines and pyrimidines go.This phenomenon is known as Chargaff’s Rule, named after Irwin Chargaff, who first noticed it. This complementary pairing occurs because the respective sizes of the bases and because of the kinds of hydrogen bonds that are possible between them (they pair more favorably with bases with which they can have the maximum amount of hydrogen bonds)
Each DNA strand has a ‘backbone’ that is made up of a sugar-phosphate chain. Attached to each one of these sugars is a nitrogenous base that is composed of carbon and nitrogen rings. The number of rings this base has determines whether the base is a purine (two rings) or a pyrimidine (one ring). The purines on one strand of DNA form hydrogen bonds with the corresponding pyrimidines on the opposite strand of DNA , and vice versa, to hold the two strands together. Within DNA molecules, this is their most important function and is known as base pairing. Because hydrogen bonds are not as strong as covalent bonds, base pairings can easily be separated, allowing for replication and transcription.
Because purines always bind with pyrimidines – known as complementary pairing – the ratio of the two will always be constant within a DNA molecule. In other words, one strand of DNA will always be an exact complement of the other as far as purines and pyrimidines go.This phenomenon is known as Chargaff’s Rule, named after Irwin Chargaff, who first noticed it. This complementary pairing occurs because the respective sizes of the bases and because of the kinds of hydrogen bonds that are possible between them (they pair more favorably with bases with which they can have the maximum amount of hydrogen bonds)
