NucleobaseNucleobases (nitrogenous bases or 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. 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). Five nucleobases—adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical.
RibozymeRibozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozymes demonstrated that RNA can be both genetic material (like DNA) and a biological catalyst (like protein enzymes), and contributed to the RNA world hypothesis, which suggests that RNA may have been important in the evolution of prebiotic self-replicating systems.
PurinePurine is a heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines and their tautomers. They are the most widely occurring nitrogen-containing heterocycles in nature. Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney. In general, plant-based diets are low in purines.
RNA interferenceRNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by other names, including co-suppression, post-transcriptional gene silencing (PTGS), and quelling. The detailed study of each of these seemingly different processes elucidated that the identity of these phenomena were all actually RNAi. Andrew Fire and Craig C.
Phosphodiester bondIn chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is dominated by their prevalence in DNA and RNA, but phosphodiesters occur in other biomolecules, e.g. acyl carrier proteins. Phosphodiester bonds make up the backbones of DNA and RNA. The phosphate is attached to the 5' carbon. The 3' carbon of one sugar is bonded to the 5' phosphate of the adjacent sugar.
DNA replicationIn molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part of biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential.
DeoxyribozymeDeoxyribozymes, also called DNA enzymes, DNAzymes, or catalytic DNA, are DNA oligonucleotides that are capable of performing a specific chemical reaction, often but not always catalytic. This is similar to the action of other biological enzymes, such as proteins or ribozymes (enzymes composed of RNA). However, in contrast to the abundance of protein enzymes in biological systems and the discovery of biological ribozymes in the 1980s, there is only little evidence for naturally occurring deoxyribozymes.
Self-replicating machineA self-replicating machine is a type of autonomous robot that is capable of reproducing itself autonomously using raw materials found in the environment, thus exhibiting self-replication in a way analogous to that found in nature. The concept of self-replicating machines has been advanced and examined by Homer Jacobson, Edward F. Moore, Freeman Dyson, John von Neumann, Konrad Zuse and in more recent times by K.
Human evolutionHuman evolution is the evolutionary process within the history of primates that led to the emergence of Homo sapiens as a distinct species of the hominid family, which includes all the great apes. This process involved the gradual development of traits such as human bipedalism, dexterity and complex language, as well as interbreeding with other hominins (a tribe of the African hominid subfamily), indicating that human evolution was not linear but weblike.
Purine metabolismPurine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms. Purines are biologically synthesized as nucleotides and in particular as ribotides, i.e. bases attached to ribose 5-phosphate. Both adenine and guanine are derived from the nucleotide inosine monophosphate (IMP), which is the first compound in the pathway to have a completely formed purine ring system. Inosine monophosphate is synthesized on a pre-existing ribose-phosphate through a complex pathway (as shown in the figure on the right).
G-quadruplexIn molecular biology, G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. They are helical in shape and contain guanine tetrads that can form from one, two or four strands. The unimolecular forms often occur naturally near the ends of the chromosomes, better known as the telomeric regions, and in transcriptional regulatory regions of multiple genes, both in microbes and across vertebrates including oncogenes in humans.
PolynucleotideIn molecular biology, a polynucleotide () is a biopolymer composed of 13 nucleotide monomers, covalently bonded in a chain. DNA (deoxyribonuc and RNA (ribonucleic acid) are examples of polynucleotides with distinct Although DNA and RNA do not generally occur in the same polynucleotide, the four species of nucleotides may occur in any order in the chain. The sequence of DNA or RNA species for a given polynucleotide is the main factor determining its function in a living organism or a scientific experiment.
