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The chemical structure of DNA base-pairs . A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA.
Some DNA- or RNA-binding enzymes can recognize specific base pairing patterns that identify particular regulatory regions of genes. Hydrogen bonding is the chemical mechanism that underlies the base-pairing rules described above. Appropriate geometrical correspondence of hydrogen bond donors and acceptors allows only the "right" pairs to form ...
Each of the base pairs in a typical double-helix DNA comprises a purine and a pyrimidine: either an A paired with a T or a C paired with a G. These purine-pyrimidine pairs, which are called base complements, connect the two strands of the helix and are often compared to the rungs of a ladder. Only pairing purine with pyrimidine ensures a ...
The base complement A = T shares two hydrogen bonds, while the base pair G ≡ C has three hydrogen bonds. All other configurations between nucleobases would hinder double helix formation. DNA strands are oriented in opposite directions, they are said to be antiparallel. [1]
A diagram of DNA base pairing, demonstrating the basis for Chargaff's rules. Chargaff's rules (given by Erwin Chargaff) state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine.
A purine base always pairs with a pyrimidine base (guanine (G) pairs with cytosine (C) and adenine (A) pairs with thymine (T) or uracil (U)). DNA's secondary structure is predominantly determined by base-pairing of the two polynucleotide strands wrapped around each other to form a double helix. Although the two strands are aligned by hydrogen ...
This arrangement of two nucleotides binding together across the double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with high GC-content is more stable than DNA with low GC-content. A Hoogsteen base pair (hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. [26]
Chemical structures for Watson–Crick and Hoogsteen A•T and G•C+ base pairs. The Hoogsteen geometry can be achieved by purine rotation around the glycosidic bond (χ) and base-flipping (θ), affecting simultaneously C8 and C1 ′ (yellow). [1] A Hoogsteen base pair is a variation of base-pairing in nucleic acids such as the A