What is "base pair"

base pair \base" pair`\ (b[=a]s" p[^a]r`), n. (Biochemistry, Genetics) a unit of double-stranded DNA or RNA consisting of two complementary bases on opposing strands of the double-stranded polynucleotide, bound together by hydrogen bonds and other non-covalent chemical forces. The bases comprising the base pairs are adenine, thymine, cytidine, and guanine. In normal DNA, the base adenine on one strand of DNA pairs with thymine on the opposite strand, and cytosine on one strand pairs with guanine on the opposite strand. The term base pair usually includes the sugar (ribose or deoxyribose) and the phosphate bound to each base to form a nucleotide unit. One base pair is sometimes used as a unit of length or size for DNA, and in this usage is abbreviated bp; as, a 100-bp fragment of DNA. A length of 1000 base pairs is a kilobase pair or kbp.

alt. (context biology English) In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds. n. (context biology English) In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds.

n. one of the pairs of chemical bases joined by hydrogen bonds that connect the complementary strands of a DNA molecule or of an RNA molecule that has two strands; the base pairs are adenine with thymine and guanine with cytosine in DNA and adenine with uracil and guanine with cytosine in RNA

A base pair (bp) is a unit 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. Dictated by specific hydrogen bonding patterns, Watson-Crick base pairs ( guanine- cytosine and adenine- thymine) allow the DNA helix to maintain a regular helical structure that is subtly dependent on its nucleotide sequence. The complementary nature of this based-paired structure provides a backup copy of all genetic information encoded within double-stranded DNA. The regular structure and data redundancy provided by the DNA double helix make DNA well suited to the storage of genetic information, while base-pairing between DNA and incoming nucleotides provides the mechanism through which DNA polymerase replicates DNA, and RNA polymerase transcribes DNA into RNA. Many DNA-binding proteins can recognize specific base pairing patterns that identify particular regulatory regions of genes.

Intramolecular base pairs can occur within single-stranded nucleic acids. This is particularly important in RNA molecules (e.g., transfer RNA), where Watson-Crick base pairs (G-C and A-U) permit the formation of short double-stranded helices, and a wide variety of non-Watson-Crick interactions (e.g., G-U or A-A) allow RNAs to fold into a vast range of specific three-dimensional structures. In addition, base-pairing between transfer RNA (tRNA) and messenger RNA (mRNA) forms the basis for the molecular recognition events that result in the nucleotide sequence of mRNA becoming translated into the amino acid sequence of proteins via the genetic code.

The size of an individual gene or an organism's entire genome is often measured in base pairs because DNA is usually double-stranded. Hence, the number of total base pairs is equal to the number of nucleotides in one of the strands (with the exception of non-coding single-stranded regions of telomeres). The haploid human genome (23 chromosomes) is estimated to be about 3.2 billion bases long and to contain 20,000–25,000 distinct protein-coding genes. A kilobase (kb) is a unit of measurement in molecular biology equal to 1000 base pairs of DNA or RNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 10, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).