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base pair (b.p., bp),
the complex of two heterocyclic nucleic acid bases, one a pyrimidine and the other a purine, brought about by hydrogen bonding between the purine and the pyrimidine; base pairing is the essential element in the structure of DNA proposed by J. Watson and F. Crick in 1953; usually guanine is paired with cytosine (G·C), and adenine with thymine (A·T) or uracil (A·U).
A pair of nitrogenous bases, consisting of a purine linked by hydrogen bonds to a pyrimidine, that connects the complementary strands of DNA or of hybrid molecules joining DNA and RNA. The base pairs are adenine-thymine and guanine-cytosine in DNA, and adenine-uracil and guanine-cytosine in RNA.
a pair of nucleotides in the complementary strands of a DNA molecule that interact through hydrogen bonding across the axis of the helix. One of the nucleotides in each pair is a purine (either adenine or guanine), and the other is a pyrimidine (either thymine or cytosine). Because of distinct hydrogen bonding capacity, adenine always pairs with thymine, and guanine always pairs with cytosine.
base pairThe structure formed between 2 complementary nitrogenous bases—purines and pyrimidines—which are hydrogen-bonded (guanine and cytosine share 3 hydrogen bonds; adenine and thymine share 2) to form double-stranded nucleic acids—DNA or RNA.
BPs are held together by weak hydrogen bonds; in double-stranded nucleic acids (DNA, RNA), purines (adenine and guanine) bond to their complementary opposites, pyrimidines (cytosine thymine, uracil)—under normal circumstances, adenine binds to thymine (DNA) or to uracil (RNA), and guanine binds to cytosine (DNA and RNA).
base pair(bās pār)
The complex of two heterocyclic nucleic acid bases, one a pyrimidine and the other a purine, brought about by hydrogen bonding between the purine and the pyrimidine; base pairing is the essential element in the structure of DNA. Usually guanine is paired with cytosine (G·C), and adenine with thymine (A·T) or uracil (A·U). The sequence of the complementary bases in either strand of a two-stranded DNA molecule codes for amino acids used in the manufacture of proteins. Trios of bases (codons) specify each of 20 amino acids. During protein synthesis (translation), messenger RNA and ribosomes read the order of amino acids from strings of DNA to create protein chains, which are then released into the cell.
base pairTwo linked molecules, one a purine the other a pyrimidine, that lie across between the two strands of the DNA double helix. The bases are linked by easily-broken hydrogen bonds and the linkage occurs only in a particular, complementary, way-adenine with thymine and guanine with cytosine. This is the essence of DNA replication, which starts with the separation of a length of the two strands at bonds. In RNA, uracil replaces thymine and adenine links with it. Distance along a DNA sequence is measured as the number of base pairs.
base pair (bp)in double-stranded NUCLEIC ACID molecules, a pair of complementary NUCLEOTIDES: in DNA, A-T and G-C; in RNA, A-U and G-C, with one nucleotide contributed from each strand of the DUPLEX. The pair of bases is held together by HYDROGEN BONDS. The length of a double-stranded nucleic acid molecule is measured in base pairs. See also COMPLEMENTARY BASE PAIRING.
1. the lowest part or foundation of anything. See also basis.
2. the main ingredient of a compound.
3. a molecule or ion with a tendency to take up a proton according to Bronsted and Lowry theory; a substance that combines with acids to form salts. In the chemical processes of the body, bases are essential to the maintenance of a normal acid-base balance. Excessive concentration of bases in the body fluids leads to alkalosis. See also basal.
4. the primary entity against which all other entities are compared.
5. the non-sugar components of nucleotides in DNA and RNA.
the two molecules forming the matching acid and conjugate base.
refers to the relative components of a nucleic acid.
the anion or uncharged molecule of an acid once it has given up its proton, e.g. Cl− is the conjugate base of the acid, HCl.
see base excess (below).
the amount of acid or base required to titrate a sample of whole arterial blood to the normal pH of 7.4. The base excess is determined mathematically by calculations that include measurement of the blood Pco2 and pH and take into account the hemoglobin level. It is negative (base deficit) in acidosis and positive in alkalosis.
the wide dorsal part of the heart carrying the atria and the large blood vessels and the attachment to the pericardial sac.
the widest part of the horn, at its attachment to the skin. In the adult horned animal the horn is hollow at this point, encloses the horn process of the frontal bone and merges with the skin. This is covered with a thin layer of horn similar to the periople of the hoof, called the epiceras.
a mandible which is narrow relative to the maxilla; often causes the lower canine teeth to strike the hard palate. See also anisognathism.
an aromatic, nitrogen-containing molecule that serves as a proton acceptor, e.g. purine or pyrimidine.
faces cranially and to the left where it is attached to the reticulum and the abomasum at the reticulo-omasal and omasoabomasal orifices.
two hydrogen bonded nucleotides in a DNA or RNA molecule.
a group of compounds of which purine is the base, including uric acid, adenine, guanine, xanthine and theobromine.
a group of chemical compounds of which pyrimidine is the base, including uracil, thymine and cytosine, which are common constituents of nucleic acids.
the footplate of the stapes in the middle ear from which the two legs originate. The stapes lies horizontally with the base facing medially and attached to the vestibular window by the annular ligament.