Complementary Definition (Biology)So, for example, the complement of guanine is cytosine because that's the base that would pair with guanine; the complement of cytosine is guanine. This is true along the entire DNA strand, which is why the two strands of DNA are called complementary strands.
Complementary base pairing is the phenomenon where in DNA guanine always hydrogen bonds to cytosine and adenine always binds to thymine. The bond between guanine and cytosine shares three hydrogen bonds compared to the A-T bond which always shares two hydrogen bonds.
Chargaff's rule, also known as the complementary base pairing rule, states that DNA base pairs are always adenine with thymine (A-T) and cytosine with guanine (C-G). A purine always pairs with a pyrimidine and vice versa.
”'complementary base pairing. The standard arrangement of bases in nucleotides in relation to their opposite pairing, such as thymine being paired with adenine and cytosine paired with guanine.
DNA and RNA base pair complementarity
| Nucleic Acid | Nucleobases | Base complement |
|---|
| DNA | adenine(A), thymine(T), guanine(G), cytosine(C) | A=T, G≡C |
| RNA | adenine(A), uracil(U), guanine(G), cytosine(C) | A=U, G≡C |
The four bases that make up this code are adenine (A), thymine (T), guanine (G) and cytosine (C). Bases pair off together in a double helix structure, these pairs being A and T, and C and G. RNA doesn't contain thymine bases, replacing them with uracil bases (U), which pair to adenine1.
mRNA → DNAFor converting a sequence from mRNA to the original DNA code, apply the rules of complementary base pairing: Cytosine (C) is replaced with Guanine (G) – and vice versa. Uracil (U) is replaced by Adenine (A) Adenine (A) is replaced by Thymine (T)
Of the many types of RNA, the three most well-known and most commonly studied are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), which are present in all organisms.
These chemical bonds act like rungs in a ladder and help hold the two strands of DNA together. There are four nucleotides, or bases, in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). These bases form specific pairs (A with T, and G with C).
Uracil is energetically less expensive to produce than thymine, which may account for its use in RNA. In DNA, however, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient.
Thymine is one of the building blocks of DNA. And in the double helix, thymine pairs with adenine, or the A nucleotide.
The base pairing rule is that adenine always is with thymine and guanine always bonds to cytosine.
The rules of base pairing explain the phenomenon that whatever the amount of adenine (A) in the DNA of an organism, the amount of thymine (T) is the same (called Chargaff's rule). Similarly, whatever the amount of guanine (G), the amount of cytosine (C) is the same.
RNA is a unique polymer. Like DNA, it can bind with great specificity to either DNA or another RNA through complementary base pairing. It can also bind specific proteins or small molecules, and, remarkably, RNA can catalyze chemical reactions, including joining amino acids to make proteins.
Base pairs are found in double-stranded DNA and RNA, where the bonds between them connect the two strands, making the double-stranded structures possible. Base pairs themselves are formed from bases, which are complementary nitrogen-rich organic compounds known as purines or pyrimidines.
In DNA, the code letters are A, T, G, and C, which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine.
A central tenet of molecular biology states that the flow of genetic information in a cell is from DNA through RNA to proteins: “DNA makes RNA makes protein”.
: completing something else or making it better : serving as a complement. —used of two things when each adds something to the other or helps to make the other better. : going together well : working well together.
Complementary sequence: Nucleic acid sequence of bases that can form a double- stranded structure by matching base pairs. For example, the complementary sequence to C-A-T-G (where each letter stands for one of the bases in DNA) is G-T-A-C.
RNA is synthesized from DNA by an enzyme known as RNA polymerase during a process called transcription. The new RNA sequences are complementary to their DNA template, rather than being identical copies of the template. RNA is then translated into proteins by structures called ribosomes.
The nitrogen bases can only pair in a certain way: A pairing with T and C pairing with G. Due to the base pairing, the DNA strands are complementary to each other, run in opposite directions, and are called antiparallel strands.
During the process of transcription, the information stored in a gene's DNA is passed to a similar molecule called RNA (ribonucleic acid) in the cell nucleus. A type of RNA called transfer RNA (tRNA) assembles the protein, one amino acid at a time.
Messenger RNA (mRNA) is a subtype of RNA. During the transcription process, a single strand of DNA is decoded by RNA polymerase, and mRNA is synthesized. Physically, mRNA is a strand of nucleotides known as ribonucleic acid, and is single-stranded.
Complementary DNA (cDNA) is a DNA copy of a messenger RNA (mRNA) molecule produced by reverse transcriptase, a DNA polymerase that can use either DNA or RNA as a template. From: Encyclopedia of Genetics, 2001.
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. Transcription ends in a process called termination.
The if given the base sequence for one strand: 5'-AGGTCCG-3', the complimentary strand must have the sequence: 3'-TCCAGGC-5'. This ensures that A only pairs with T, and C only pairs with G.
