A report on Base pair and Pyrimidine

Depiction of the adenine–thymine Watson–Crick base pair
Pinner's 1885 structure for pyrimidine
The pyrimidine nitrogen bases found in DNA and RNA.

The bigger nucleobases, adenine and guanine, are members of a class of double-ringed chemical structures called purines; the smaller nucleobases, cytosine and thymine (and uracil), are members of a class of single-ringed chemical structures called pyrimidines.

- Base pair

These hydrogen bonding modes are for classical Watson–Crick base pairing.

- Pyrimidine
Depiction of the adenine–thymine Watson–Crick base pair

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Base pairing: Two base pairs are produced by four nucleotide monomers, nucleobases are in blue. Guanine (G) is paired with cytosine (C) via three hydrogen bonds, in red. Adenine (A) is paired with uracil (U) via two hydrogen bonds, in red.

Nucleobase

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Nucleobases, also known as nitrogenous bases or often simply bases, are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids.

Nucleobases, also known as nitrogenous bases or often simply bases, are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids.

Base pairing: Two base pairs are produced by four nucleotide monomers, nucleobases are in blue. Guanine (G) is paired with cytosine (C) via three hydrogen bonds, in red. Adenine (A) is paired with uracil (U) via two hydrogen bonds, in red.
Purine nucleobases are fused-ring molecules.
Pyrimidine nucleobases are simple ring molecules.
Chemical structure of DNA, showing four nucleobase pairs produced by eight nucleotides: adenine (A) is joined to thymine (T), and guanine (G) is joined to cytosine (C). + This structure also shows the directionality of each of the two phosphate-deoxyribose backbones, or strands. The 5' to 3' (read "5 prime to 3 prime") directions are: down the strand on the left, and up the strand on the right. The strands twist around each other to form a double helix structure.

The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Similarly, the simple-ring structure of cytosine, uracil, and thymine is derived of pyrimidine, so those three bases are called the pyrimidine bases.

The structure of the DNA double helix. The atoms in the structure are colour-coded by element and the detailed structures of two base pairs are shown in the bottom right.

DNA

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Polymer composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.

Polymer composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.

The structure of the DNA double helix. The atoms in the structure are colour-coded by element and the detailed structures of two base pairs are shown in the bottom right.
Chemical structure of DNA; hydrogen bonds shown as dotted lines. Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3' hydroxyl group (—OH) on the other.
A section of DNA. The bases lie horizontally between the two spiraling strands ([[:File:DNA orbit animated.gif|animated version]]).
DNA major and minor grooves. The latter is a binding site for the Hoechst stain dye 33258.
From left to right, the structures of A, B and Z DNA
DNA quadruplex formed by telomere repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix. The green spheres in the center represent potassium ions.
A covalent adduct between a metabolically activated form of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA
Location of eukaryote nuclear DNA within the chromosomes
T7 RNA polymerase (blue) producing an mRNA (green) from a DNA template (orange)
DNA replication: The double helix is unwound by a helicase and topo­iso­merase. Next, one DNA polymerase produces the leading strand copy. Another DNA polymerase binds to the lagging strand. This enzyme makes discontinuous segments (called Okazaki fragments) before DNA ligase joins them together.
Interaction of DNA (in orange) with histones (in blue). These proteins' basic amino acids bind to the acidic phosphate groups on DNA.
The lambda repressor helix-turn-helix transcription factor bound to its DNA target
The restriction enzyme EcoRV (green) in a complex with its substrate DNA
Recombination involves the breaking and rejoining of two chromosomes (M and F) to produce two rearranged chromosomes (C1 and C2).
The DNA structure at left (schematic shown) will self-assemble into the structure visualized by atomic force microscopy at right. DNA nanotechnology is the field that seeks to design nanoscale structures using the molecular recognition properties of DNA molecules.
Maclyn McCarty (left) shakes hands with Francis Crick and James Watson, co-originators of the double-helix model.
Pencil sketch of the DNA double helix by Francis Crick in 1953
A blue plaque outside The Eagle pub commemorating Crick and Watson
Impure DNA extracted from an orange

The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA.

The complementary nitrogenous bases are divided into two groups, pyrimidines and purines.

Chemical structure of uridine

Uracil

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One of the four nucleobases in the nucleic acid RNA that are represented by the letters A, G, C and U. The others are adenine (A), cytosine (C), and guanine (G).

One of the four nucleobases in the nucleic acid RNA that are represented by the letters A, G, C and U. The others are adenine (A), cytosine (C), and guanine (G).

Chemical structure of uridine

Uracil is a common and naturally occurring pyrimidine derivative.

In RNA, uracil base-pairs with adenine and replaces thymine during DNA transcription.

Thymine

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One of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T.

One of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T.

Thymine is also known as 5-methyluracil, a pyrimidine nucleobase.

The mutations caused by thymine deficiency appear to occur only at AT base pair sites in DNA and are often AT to GC transition mutations.

A hairpin loop from a pre-mRNA. Highlighted are the nucleobases (green) and the ribose-phosphate backbone (blue). This is a single strand of RNA that folds back upon itself.

RNA

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Polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes.

Polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes.

A hairpin loop from a pre-mRNA. Highlighted are the nucleobases (green) and the ribose-phosphate backbone (blue). This is a single strand of RNA that folds back upon itself.
Three-dimensional representation of the 50S ribosomal subunit. Ribosomal RNA is in ochre, proteins in blue. The active site is a small segment of rRNA, indicated in red.
Watson-Crick base pairs in a siRNA (hydrogen atoms are not shown)
Structure of a fragment of an RNA, showing a guanosyl subunit.
Secondary structure of a telomerase RNA.
Structure of a hammerhead ribozyme, a ribozyme that cuts RNA
Uridine to pseudouridine is a common RNA modification.
Double-stranded RNA
Robert W. Holley, left, poses with his research team.

Adenine and guanine are purines, cytosine and uracil are pyrimidines.

This antisense-based process involves steps that first process the RNA so that it can base-pair with a region of its target mRNAs.

Cytosine

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One of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA).

One of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA).

It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2).

In Watson-Crick base pairing, it forms three hydrogen bonds with guanine.

Nucleic acids RNA (left) and DNA (right).

Nucleic acid

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Nucleic acids are biopolymers, macromolecules, essential to all known forms of life.

Nucleic acids are biopolymers, macromolecules, essential to all known forms of life.

Nucleic acids RNA (left) and DNA (right).
The Swiss scientist Friedrich Miescher discovered nucleic acid first naming it as nuclein, in 1868. Later, he raised the idea that it could be involved in heredity.

Using amino acids and the process known as protein synthesis, the specific sequencing in DNA of these nucleobase-pairs enables storing and transmitting coded instructions as genes.

Each nucleotide consists of three components: a purine or pyrimidine nucleobase (sometimes termed nitrogenous base or simply base), a pentose sugar, and a phosphate group which makes the molecule acidic.

Match up between two DNA bases (guanine and cytosine) showing hydrogen bonds (dashed lines) holding them together

Complementarity (molecular biology)

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In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle.

In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle.

Match up between two DNA bases (guanine and cytosine) showing hydrogen bonds (dashed lines) holding them together
Match up between two DNA bases (adenine and thymine) showing hydrogen bonds (dashed lines) holding them together
Complementarity between two antiparallel strands of DNA. The top strand goes from the left to the right and the lower strand goes from the right to the left lining them up.
Left: the nucleotide base pairs that can form in double-stranded DNA. Between A and T there are two hydrogen bonds, while there are three between C and G. Right: two complementary strands of DNA.
A sequence of RNA that has internal complementarity which results in it folding into a hairpin
A sequence of RNA showing hairpins (far right and far upper left), and internal loops (lower left structure)
Formation and function of miRNAs in a cell

The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together.

Adenine and guanine are purines, while thymine, cytosine and uracil are pyrimidines.