Base pairing

In the building blocks of the DNA double helix, base pairing contributes to the interior structure of RNA and DNA. In order to maintain the helical structure of the constant that is independent of the nucleotide sequence, the hydrogen bonds to allow the DNA strand, Watson – is determined by the specific pattern (thymine – – adenine and cytosine guanine) Crick base pairs. Complementary nature of the base pair structure provides a backup copy of all genetic information encoded in double-stranded DNA. Data redundancy and regular structure provided by the double helix DNA DNA, which has been made suitable for the storage of genetic information, base pairing received between nucleotides and DNA can replicate DNA is DNA polymerase However, to provide a mechanism for RNA polymerase transcribing DNA into RNA. DNA binding proteins, many can recognize a specific pattern of a pair of specific type specific regulatory region of the gene.

Base pairing

Intramolecular base pairing may occur in single-stranded nucleic acid. (E.g., AA or GU) to allow the various interactions of the click, Watson – – Non-Watson and formation of the double helical short chain This includes a (AS and GC) Crick base pairs, RNA molecules (e.g. , RNA is particularly important in transfer RNA), can be folded into a wide range of three-dimensional structure of a particular. Further, between messenger RNA base pairing transcribed RNA and the (tRNA) and (mRNA), as a result of the base sequence of mRNA underlying molecular recognition events, was translated into the amino acid sequence of the protein.

The DNA, because it is a double-stranded Generally, in many cases, the size of the entire genome of an organism or individual genes is measured in base pairs. Therefore, the number of base pairs in all is the number of nucleotides in (excluding non-coding region of one strand telomere) one of the wires. Estimates (23 chromosomes) long and about 3.2 billion base pairs in the haploid human genome, and contains the different genes from 25.000 to 20.000. Kilobases (KB) is a unit of molecular biology equal to 1000 base pairs of RNA or DNA.

In the double helix of DNA, each type of nucleic acid base of base 1 chain link on the only other circuits. This is called an auxiliary base pairs. Here, purines form hydrogen bonds thymine, adenine, pyrimidine gluing guanine cytosine bonded by hydrogen bonds only three hydrogen bonds and only two. This arrangement of two nucleotide binding, is called base pairs in the double helix. Hydrogen bond is not a covalent bond, it is possible to separate them, and recombine relatively easily. Both strands of the DNA double helix, you can zip by, or to open by high temperature and mechanical forces. As a result of this complementarity, all information in the helices of the two-stranded DNA sequence repeats every section is essential for DNA replication. Indeed, a specific interaction with this reversible, is important for all functions of DNA in living organisms between complementary base pairs.

Base pairing Adenine Thymine
Top with three hydrogen bonds 3, GC base pairs. It is an AT base pair with two hydrogen bonds down. Non-covalent bonds between pairs, hydrogen bonds are shown in dashed lines. The two types of base pairs to form two hydrogen bonds (with reference to FIG, right) GC to form three hydrogen bonds number of hydrogen bonds are different. DNA of high GC content are more stable than DNA GC content is low. As mentioned above, most of the DNA molecule is a polymer two fibers bound together in a spiral shape by non-covalent bonds in fact, the double-stranded structure (double-stranded DNA), the intrastrand base stacking mutual G, and C is the strongest stack by the action is maintained substantially. I to form single-stranded DNA molecules of a single (single stranded DNA) molecules – a process known as melt – that the two filaments may be dissolved. Melting high pH high temperature, and low salt (or low pH is, melt the DNA, but since DNA is unstable to acid depurination, low pH is rarely used) is done in.

The double-stranded DNA, as well as to (% G, C base pairs) to the content of GC (in the order specified in the configuration), the stability of the foam is dependent not only sequences, long length ( molecule is more stable). It can be measured in various ways, in the conventional method is a “melting point” is the temperature 50% of the molecules are converted to DS SS molecular stability; melting temperature, DNA concentration and ionic strength I depend on. As a result, it is the sum of the length of the DNA double helix which determines the strength of the relationship between two strands of DNA and percentage of GC base pairs. Long chain DNA with high GC content has a strong interaction strand, I have a chain of weak interaction is short filaments of high strength. In biology, the part of the double helix of DNA that must be removed easily by Puribu box TATAAT in the promoter of some, tend to have threads to decompose the high content AT easily.

In the laboratory, the strength of this interaction can be measured by finding the temperature required it hydrogen bonds to break (Tm called value) to their melting point. Base pairs of all of the double helix strand melting in the DNA, when present in isolation in solution as a molecule completely separate the two. Single-stranded DNA molecules of these (single-stranded DNA) are not in common shape, but conformation Some are more stable than others.

Hydrogen bond is a chemical reaction is based on base-pairing rules discussed above. Only response appropriate geometric acceptor and hydrogen bond donor “to correct” pair, it is possible to form a solid. Stable than DNA with higher GC content, but, contrary to popular belief, hydrogen bonding significantly, and to stabilize the DNA, DNA GC content is high is is due to stacking interaction stability does not.

Is a member of a class is a member of a class of chemical structure of a double annular called purine larger nucleobases adenine, and guanine, less nucleotide bases, thymine and cytosine (uracil), and the chemical cyclic structure called pyrimidine . Are supplemented with pyrimidine purine: pyrimidine – is disadvantageous vigorously pyrimidine pair, because the molecules are too far apart for hydrogen bonding, resulting molecule is too close, a pair of pudding pudding The overlap with the repulsive force can be but it is disadvantageous vigorously, to establish. Or pairing purine pyrimidine bases result of dual structure of appropriate GC. Hydrogen donor and pattern of the receptor does not support, pudding only other – pyrimidine lot is the (RNA) UA GT and the AC, but these pairs are mismatched. Hydrogen bonds, two GU pairing occurs quite often (see wobble base pairs) RNA.

DNA and RNA molecules in a pair are relatively stable at room temperature, the length of the molecule, nucleotides two isolated above the melting point to be determined by the content GC (if any), and the degree of mismatch to. The genome of Thermus extreme it like organisms, GC-rich thermo particularly that, therefore, high GC content leading to a higher melting temperature, is surprising. Conversely, the region of the genome that are peeling frequently – for example, the promoter region of a gene, transcription – often relatively poor GC-(see, for example, TATA box). It must also be considered the melting temperature and GC content when designing the primers for the PCR reaction