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glycolipid Any of a subclass of lipids consisting of a central polar molecule (most commonly glycerol or sphingosine) which is covalently attached to one or more monosaccharides or oligosaccharides via glycosidic bonds, as well as to one or more long, non-polar fatty acid chains. Glycolipids are one of three major type... | Wikipedia - Glossary of cellular and molecular biology (0–L) - G | 348 | 1,466 | null |
Proteins exposed on the outer surface of the plasma membrane or secreted into the extracellular space are commonly modified in this way, after which they are said to be glycosylated. glycosidase Any of a class of enzymes capable of breaking one or more glycosidic bonds in carbohydrate molecules, commonly found in lysos... | Wikipedia - Glossary of cellular and molecular biology (0–L) - G | 342 | 1,317 | null |
Goldberg-Hogness box See TATA box. Golgi apparatus gRNA See guide RNA. guanine (G) A purine nucleobase used as one of the four standard nucleobases in both DNA and RNA molecules. Guanine forms a base pair with cytosine. guanine-cytosine content Also abbreviated GC-content. The proportion of nitrogenous bases in a nucle... | Wikipedia - Glossary of cellular and molecular biology (0–L) - G | 335 | 1,352 | null |
Section: H. hairpin See stem-loop. haploid Denoted in shorthand with the somatic number n. (of a cell or organism) Having one copy of each chromosome, with each copy not being part of a pair. Contrast diploid and polyploid. Hayflick limit helicase Any of a class of ATP-dependent motor proteins that move directionally a... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 347 | 1,569 | null |
heterochromatin heterochromosome See allosome. heterodimer A protein or protein domain composed of two different polypeptides which are paired with each other in the quaternary structure of a multimeric complex. Contrast homodimer. heterogeneous nuclear RNA (hnRNA) heterokaryon A multinucleate cell containing nuclei wi... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 332 | 1,542 | null |
In practice the term is sometimes used more broadly to include cytology. histone Any of a class of highly alkaline proteins responsible for packaging nuclear DNA into structural units called nucleosomes in eukaryotic cells. Histones are the chief protein components of chromatin, where they associate into eight-membered... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 350 | 1,631 | null |
homeobox Any of a class of DNA sequences approximately 180 base pairs in length occurring near the 3'‐end of certain eukaryotic genes and encoding a 60-amino acid domain, known as a homeodomain, which is capable of binding to DNA or RNA via a characteristic helix-turn-helix motif. Homeobox-containing genes are translat... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 320 | 1,560 | null |
Homeodomains are the translated versions of homeoboxes, though the terms are often used interchangeably. homodimer A protein or protein domain composed of two identical polypeptides which are paired with each other in the quaternary structure of a multimeric complex. Contrast heterodimer. homologous chromosomes Also ho... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 347 | 1,545 | null |
bacterial conjugation. housekeeping gene Any constitutive gene that is transcribed at a relatively constant level across many or all known conditions and cell types. The products of housekeeping genes typically play critical roles in the maintenance of cellular integrity and basic metabolic function. It is generally as... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 345 | 1,964 | null |
Hybrids may occur naturally or artificially, as during selective breeding of domesticated animals and plants. Reproductive barriers typically prevent hybridization between distantly related organisms, or at least ensure that hybrid offspring are sterile, but fertile hybrids may result in speciation. hybridization 1. Th... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 346 | 1,834 | null |
Together, the contrasting properties of hydrophilicity and hydrophobicity play major roles in determining the structural conformations and functions of most biomolecules. hydrophobic Sometimes used interchangeably with lipophilic. Having a low solubility in or affinity for water or other polar solvents; describing a no... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 346 | 1,828 | null |
having positive osmotic pressure, such that solvent will tend to move by osmosis across a semipermeable membrane from the solution of lower solute concentration to the solution of higher concentration until both solutions have equal concentrations. In a cell where the intracellular cytosol is hypertonic relative to the... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 286 | 1,405 | null |
having negative osmotic pressure, such that solvent will tend to move by osmosis across a semipermeable membrane from the solution of lower solute concentration to the solution of higher concentration until both solutions have equal concentrations. In a cell where the intracellular cytosol is hypotonic relative to the ... | Wikipedia - Glossary of cellular and molecular biology (0–L) - H | 218 | 1,001 | null |
Section: I. idiochromosome See allosome. idiogram Also ideogram. A diagrammatic or schematic karyotype of the entire set of chromosomes within a cell or genome, in which annotated illustrations depict each chromosome in its most idealized form (e.g. with straight lines and obvious centromeres) so as to facilitate the e... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 310 | 1,413 | null |
in silico (of a scientific experiment or research) Conducted, produced, or analyzed by means of computer modeling or simulation, as opposed to a real-world trial. in situ (of a scientific experiment or biological process) Occurring or made to occur in a natural, uncontrolled setting, or in the natural or original posit... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 348 | 1,815 | null |
in vitro (of a scientific experiment or biological process) Occurring or made to occur in a laboratory vessel or other controlled artificial environment, e.g. in a test tube or a petri dish, as opposed to inside a living organism or in a natural setting. in vivo (of a scientific experiment or biological process) Occurr... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 349 | 1,588 | null |
The term is used in particular to refer to the part of a transposable element that codes for those proteins directly involved in the transposition process, e.g. the transposase enzyme. The coding region in a transposable insertion sequence is usually flanked by short inverted repeats, and the structure of larger transp... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 345 | 1,805 | null |
Contrast integral polytopic protein. integral polytopic protein Also transmembrane protein. Any of a class of integral membrane proteins which span the entirety of the cell membrane, extending from the interior or cytosolic side of the membrane to the exterior or extracellular side. Transmembrane proteins typically hav... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 334 | 1,685 | null |
Contrast extein. intercalating agent Any chemical compound (e.g. ethidium bromide) that disrupts the alignment and pairing of bases in the complementary strands of a DNA molecule by inserting itself between the bases. intercalation The insertion, naturally or artificially, of chemical compounds between the planar bases... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 333 | 1,546 | null |
internal ribosome entry site (IRES) A sequence present in some messenger RNAs that permits recognition by the ribosome and thus the initiation of translation even in the absence of a 5' cap, which in eukaryotes is otherwise required for assembly of the initiation complex. IRES elements are often located in the 5' untra... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 330 | 1,769 | null |
Peptide sequences lacking intrinsic order are generally characterized by high proportions of charged and hydrophilic amino acids and low proportions of hydrophobic amino acids, making them inherently flexible, accessible, and modifiable, which allows the same peptide sequence to have distinct functions across a wide va... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 319 | 1,638 | null |
inverted repeat A nucleotide sequence followed downstream on the same strand by its own reverse complement. The initial sequence and the reverse complement may be separated by any number of nucleotides, or may be immediately adjacent to each other; in the latter case, the composite sequence is also called a palindromic... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 344 | 1,711 | null |
Isochromosome formation is equivalent to simultaneous duplication and deletion events such that two copies of either the long arm or the short arm comprise the resulting chromosome. isoelectric point (pH(I), pI) Also isoelectric pH. The pH at which a particular molecule, often a protein, carries no net electrical charg... | Wikipedia - Glossary of cellular and molecular biology (0–L) - I | 344 | 1,703 | null |
Section: J. jumping gene See transposable element. junctional diversity junk DNA Any DNA sequence that appears to have no known biological function, or which acts in a way that has no positive or a net negative effect on the fitness of the genome in which it is located. The term was once more broadly used to refer to a... | Wikipedia - Glossary of cellular and molecular biology (0–L) - J | 311 | 1,528 | null |
Section: K. karyogram A karyotype which depicts the entire set of chromosomes in a cell or organism by using photomicrographs of the actual chromosomes as they appear in vivo (usually during metaphase, in their most condensed forms), as opposed to the idealized illustrations of chromosomes used in idiograms. The photom... | Wikipedia - Glossary of cellular and molecular biology (0–L) - K | 322 | 1,359 | null |
karyotype The number and appearance of chromosomes within the nucleus of a eukaryotic cell, especially as depicted in an organized karyogram or idiogram (in pairs and arranged by size and by position of the centromere). The term is also used to refer to the complete set of chromosomes in a species or individual organis... | Wikipedia - Glossary of cellular and molecular biology (0–L) - K | 338 | 1,450 | null |
kilobase (kb) A unit of nucleic acid length equal to one thousand (1×103) bases in single-stranded molecules or one thousand base pairs in duplex molecules such as double-stranded DNA. kinase Any of a class of enzymes which catalyze the transfer of phosphate groups from high-energy, phosphate-donating molecules such as... | Wikipedia - Glossary of cellular and molecular biology (0–L) - K | 281 | 1,273 | null |
knob In cytogenetics, an enlarged, heavily staining chromomere that can be used as a visual marker, allowing specific chromosomes to be easily identified in the nucleus. knockdown (KD) A genetic engineering method by which the normal rate of expression of one or more of an organism's genes is reduced or suppressed (tho... | Wikipedia - Glossary of cellular and molecular biology (0–L) - K | 341 | 1,671 | null |
at specific times or in specific tissues, by linking the expression of the gene to some easily modifiable biochemical state or condition. In a heterozygous knockout, only one of a diploid organism's two alleles is knocked out; in a homozygous knockout, both copies are knocked out. Contrast knockin. Kozak consensus sequ... | Wikipedia - Glossary of cellular and molecular biology (0–L) - K | 207 | 987 | null |
Section: L. labelling Also tagging. The chemical attachment of a highly selective substance, known as a label, tag, or probe, to a particular cell, protein, amino acid, or other molecule of interest, either naturally or artificially, in vivo or in vitro. Natural labelling is a primary mechanism by which biomolecules sp... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 298 | 1,423 | null |
Because DNA polymerase works only in the 5' to 3' direction, but the lagging strand's overall direction of chain elongation must ultimately be the opposite (i.e. 3' to 5', toward the replication fork), elongation must occur by an indirect mechanism in which a primase enzyme synthesizes short RNA primers complementary t... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 345 | 1,633 | null |
lateral gene transfer (LGT) See horizontal gene transfer. leader sequence See 5' untranslated region. leading strand In DNA replication, the nascent strand for which both the direction of synthesis by DNA polymerase and the direction of overall chain elongation are toward the replication fork; i.e. both occur in the 5'... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 304 | 1,355 | null |
Recessive lethal mutations are fatal only to homozygotes, whereas dominant lethals are fatal even in heterozygotes. leucine zipper (ZIP) A common structural motif in DNA-binding transcription factors and some other types of proteins, approximately 35 amino acids in length, characterized chiefly by the recurrence of the... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 340 | 1,563 | null |
An example is DNA ligase, which catalyzes the formation of phosphodiester bonds between adjacent nucleotides on the same strand of a DNA molecule, a reaction known as ligation. ligation The joining of consecutive nucleotides in the same strand of a nucleic acid molecule via the formation of a phosphodiester bond betwee... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 328 | 1,488 | null |
linkage The tendency of DNA sequences which are physically near to each other on the same chromosome to be inherited together during meiosis. Because the physical distance between them is relatively small, the chance that any two nearby parts of a DNA sequence (often loci or genetic markers) will be separated on to dif... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 323 | 1,621 | null |
DNA molecules which are identical except for their linking numbers are known as topological isomers. lipid Any of a heterogeneous class of organic compounds, including glycerides (fats), waxes, sterols, and some vitamins, united only by their amphipathic or hydrophobic nature and consequently their very low solubility ... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 350 | 1,591 | null |
Though bilayers are sometimes colloquially described as phospholipid bilayers, phospholipids are just one of several classes of membrane lipids which form bilayers; most membranes are actually a fluid, heterogeneous mixture of phospholipids, glycolipids, and cholesterols, interspersed and studded with various other mol... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 306 | 1,326 | null |
See also long intervening non-coding RNA. lyonization See X-inactivation. lysis The disruption and decomposition of the plasma membrane surrounding a cell, or more generally of any membrane-bound organelle or vesicle, especially by osmotic, enzymatic, or other chemical or mechanical processes which compromise the membr... | Wikipedia - Glossary of cellular and molecular biology (0–L) - L | 206 | 950 | null |
Article: Glossary of cellular and molecular biology (M–Z). This glossary of cellular and molecular biology is a list of definitions of terms and concepts commonly used in the study of cell biology, molecular biology, and related disciplines, including molecular genetics, biochemistry, and microbiology. It is split acro... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - Summary | 187 | 950 | null |
Section: M. M phase See mitosis. macromolecule Any very large molecule composed of dozens, hundreds, or thousands of covalently bonded atoms, especially one with biological significance. Many important biomolecules, such as nucleic acids and proteins, are polymers consisting of a repeated series of smaller monomers; ot... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 347 | 1,671 | null |
megabase (Mb) A unit of nucleic acid length equal to one million (1×106) bases in single-stranded molecules or one million base pairs in duplex molecules such as double-stranded DNA. meiosis A specialized type of cell division that occurs exclusively in sexually reproducing eukaryotes, during which DNA replication is f... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 337 | 1,625 | null |
Certain types of lipids, specifically phospholipids and other membrane lipids, commonly occur as double-layered sheets of molecules when immersed in an aqueous environment, which can themselves assume approximately spherical shapes, acting as semipermeable barriers surrounding a water-filled interior space. This is the... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 272 | 1,354 | null |
The primary products of transcription, mRNAs are synthesized by RNA polymerase, which builds a chain of ribonucleotides that complement the deoxyribonucleotides of a DNA template; in this way, the DNA sequence of a protein-coding gene is effectively preserved in the raw transcript, which is subsequently processed into ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 310 | 1,568 | null |
metabolite An intermediate or end product of metabolism, especially degradative metabolism (catabolism); or any substance produced by or taking part in a metabolic reaction. Metabolites include a huge variety of small molecules generated by cells from various pathways and having various functions, including as inputs t... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 337 | 1,560 | null |
methylation The covalent attachment of a methyl group (–CH3) to a chemical compound, protein, or other biomolecule, either spontaneously or by enzymatic catalysis. Methylation is one of the most widespread natural mechanisms by which nucleic acids and proteins are labelled. The methylation of nucleobases in a DNA molec... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 342 | 1,568 | null |
microchromosome A type of very small chromosome, generally less than 20,000 base pairs in size, present in the karyotypes of some organisms. microdeletion A chromosomal deletion that is too short to cause any apparent change in morphology under a light microscope, though it may still be detectable with other methods su... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 350 | 1,582 | null |
microsatellite Also short tandem repeat (STR) or simple sequence repeat (SSR). A type of satellite DNA consisting of a relatively short sequence of tandem repeats, in which certain motifs (ranging in length from one to six or more bases) are repeated, typically 5–50 times. Microsatellites are widespread throughout most... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 340 | 1,478 | null |
microvillus A small, slender, tubular cytoplasmic projection, generally 0.2–4 micrometres long and 0.1 micrometres in diameter, protruding from the surface of some animal cells and supported by a central core of microfilaments. When present in large numbers, such as on epithelial cells lining the respiratory and alimen... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 329 | 1,545 | null |
minisatellite A region of repetitive, non-coding genomic DNA in which certain DNA motifs (typically 10–60 bases in length) are tandemly repeated (typically 5–50 times). In the human genome, minisatellites occur at more than 1,000 loci, especially in centromeres and telomeres, and exhibit high mutation rates and high va... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 340 | 1,501 | null |
Mistranslation may originate from a mischarged transfer RNA or from a malfunctioning ribosome. mitochondrial DNA (mtDNA) The set of DNA molecules contained within mitochondria, usually one or more circular plasmids representing a semi-autonomous genome which is physically separate from and functionally independent of t... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 343 | 1,568 | null |
The majority of the structural proteins found in mitochondria are encoded by nuclear genes, however, such that mitochondria are only partially autonomous. These observations suggest mitochondria evolved from symbiotic prokaryotes living inside eukaryotic cells. mitogen Any substance or stimulus that promotes or induces... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 332 | 1,542 | null |
mitotic index (MI) The proportion of cells within a sample which are undergoing mitosis at the time of observation, typically expressed as a percentage or as a value between 0 and 1. The number of cells dividing by mitosis at any given time can vary widely depending on organism, tissue, developmental stage, and culture... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 343 | 1,716 | null |
more than one number of sets of chromosomes, in different cells of the same cellular population. mobile genetic element (MGE) Any genetic material that can move between different parts of a genome or be transferred from one species or replicon to another within a single generation. The many types of MGEs include transp... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 314 | 1,642 | null |
molecular cloning Any of various molecular biology methods designed to replicate a particular molecule, usually a DNA sequence or a protein, many times inside the cells of a natural host. Commonly, a recombinant DNA fragment containing a gene of interest is ligated into a plasmid vector, which competent bacterial cells... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 342 | 1,621 | null |
Contrast dicentric and holocentric. monoclonal Describing cells, proteins, or molecules descended or derived from a single clone (i.e. from the same genome or genetic lineage) or made in response to a single unique compound. Monoclonal antibodies are raised against only one antigen or can only recognize one unique epit... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 348 | 1,553 | null |
With few exceptions, all monosaccharides are variations on the empirical formula (CH2O)n, where n typically ranges from 3 (trioses) to 7 (heptoses). Common examples include glucose, ribose, and deoxyribose. monosomy The abnormal and frequently pathological presence of only one chromosome of a normal diploid pair. It is... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 309 | 1,406 | null |
mosaicism The presence of two or more populations of cells with different genotypes in an individual organism which has developed from a single fertilized egg. A mosaic organism can result from many kinds of genetic phenomena, including nondisjunction of chromosomes, endoreduplication, or mutations in individual stem c... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 345 | 1,708 | null |
Contrast unicellular. multinucleate (of a cell) Having more than one nucleus within a single cell; i.e. having multiple nuclei occupying the same cytoplasm. multiomics multiple cloning site (MCS) Also polylinker. mutagen Any physical or chemical agent that changes the genetic material (usually DNA) of an organism and t... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - M | 336 | 1,664 | null |
Section: N. n orientation One of two possible orientations by which a linear DNA fragment can be inserted into a vector, specifically the one in which the gene maps of both fragment and vector have the same orientation. Contrast u orientation. NAD See nicotinamide-adenine dinucleotide. NADP See nicotinamide-adenine din... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 337 | 1,626 | null |
negative (-) sense strand See template strand. negative control Also negative regulation. The inhibition or deactivation of some biological process caused by the presence of a specific molecular entity (e.g. a repressor), in the absence of which the process is not inhibited and thus can proceed normally. In gene regula... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 320 | 1,474 | null |
Nicks may be caused by DNA damage or by dedicated nucleases known as nicking enzymes, which nick DNA at random or specific sites. Nicks are frequently placed by the cell as markers identifying target sites for enzyme activity, including in DNA replication, transcription, and mismatch repair, and also to release torsion... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 328 | 1,546 | null |
Many of the best known naturally occurring ncAAs occur as intermediates in the metabolic pathways leading to the standard amino acids, while others have been made synthetically in the laboratory. non-coding DNA (ncDNA) Any segment of DNA that does not encode a sequence that may ultimately be transcribed and translated ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 338 | 1,595 | null |
It may be caused by a variety of factors. non-homologous end joining (NHEJ) nonrepetitive sequence Broadly, any nucleotide sequence or region of a genome that does not contain repeated sequences, or in which repeats do not comprise a majority; or any segment of DNA exhibiting the reassociation kinetics expected of a un... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 347 | 1,644 | null |
N-terminus Also amine terminus and amino terminus. The end of a linear chain of amino acids (i.e. a peptide) that is terminated by the free amine group (–NH2) of the first amino acid added to the chain during translation. This amino acid is said to be N-terminal. By convention, sequences, domains, active sites, or any ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 311 | 1,557 | null |
Even though all adult somatic cells have the same set of genes, cells can nonetheless differentiate into distinct cell types by expressing different subsets of these genes. Though this principle generally holds true, the reality is slightly more complex, as mutations such as insertions, deletions, duplications, and tra... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 346 | 1,784 | null |
nuclear pore A complex of membrane proteins that creates an opening in the nuclear envelope through which certain molecules and ions are permitted to pass and thereby enter or exit the nucleus (analogous to the channel proteins in the cell membrane). The nuclear envelope typically has thousands of pores to selectively ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 350 | 1,641 | null |
nuclease Any of a class of enzymes capable of cleaving phosphodiester bonds connecting adjacent nucleotides in a nucleic acid molecule (the opposite of a ligase). Nucleases may nick one strand or cut both strands of a duplex molecule, and may cleave randomly or at specific recognition sequences. They are ubiquitous and... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 337 | 1,645 | null |
nucleobase Sometimes used interchangeably with nitrogenous base or simply base. Any of the five primary or canonical nitrogenous bases – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) – that form nucleosides and nucleotides, the latter of which are the fundamental building blocks of nucleic acids. ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 335 | 1,371 | null |
nucleoplasm Also karyoplasm. All of the material enclosed within the nucleus of a cell by the nuclear envelope, analogous to the cytoplasm enclosed by the main cell membrane. Like the cytoplasm, the nucleoplasm is composed of a gel-like substance (the nucleosol) in which various organelles, nuclear proteins, and other ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 326 | 1,328 | null |
nucleosome The basic structural subunit of chromatin used in packaging nuclear DNA such as chromosomes, consisting of a core particle of eight histone proteins around which double-stranded DNA is wrapped in a manner akin to thread wound around a spool. The technical definition of a nucleosome includes a segment of DNA ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 336 | 1,572 | null |
An organic molecule that serves as the fundamental monomer or subunit of nucleic acid polymers, including RNA and DNA. Each nucleotide is composed of three connected functional groups: a nitrogenous base, a five-carbon sugar (either ribose or deoxyribose), and a single phosphate group. Though technically distinct, the ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - N | 264 | 1,263 | null |
Section: O. occluding junction ochre One of three stop codons used in the standard genetic code; in RNA, it is specified by the nucleotide triplet UAA. The other two stop codons are named amber and opal. Okazaki fragments Short sequences of nucleotides which are synthesized discontinuously by DNA polymerase and later l... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - O | 343 | 1,491 | null |
In the laboratory, oligonucleotides are commonly used as primers or hybridization probes to detect the presence of larger mRNA molecules or assembled into two-dimensional microarrays for high-throughput sequencing analysis. oligosaccharide A polymeric carbohydrate molecule consisting of a relatively short chain of conn... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - O | 317 | 1,411 | null |
The other two stop codons are named amber and ochre. open chromatin See euchromatin. open reading frame (ORF) The part of a reading frame that has the ability to be translated from DNA or RNA into protein; any continuous stretch of codons that contains a start codon and a stop codon. operator A regulatory sequence with... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - O | 317 | 1,603 | null |
Organelles occur in both prokaryotic and eukaryotic cells. In the latter they are often separated from the cytoplasm by being enclosed with their own membrane bilayer (whence the term membrane-bound organelles), though organelles may also be functionally specific areas or structures without a surrounding membrane; some... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - O | 297 | 1,388 | null |
Physiological dysfunction caused by a sudden change in the concentration of dissolved solutes in the extracellular environment surrounding a cell, which provokes the rapid movement of water across the cell membrane by osmosis, either into or out of the cell. In a severely hypertonic environment, where extracellular sol... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - O | 349 | 1,677 | null |
Section: P. p53 Also Tumor protein P53 (TP53), transformation-related protein 53 (TRP53), and cellular tumor antigen p53. A class of regulatory proteins encoded by the TP53 gene in vertebrates which bind DNA and regulate gene expression in order to protect the genome from mutation and block progression through the cell... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 339 | 1,463 | null |
paracellular transport The transfer of substances across an epithelium by passing through the extracellular space between cells, in contrast to transcellular transport, where substances travel through cells by crossing the intracellular cytoplasm. paracrine Describing or relating to a class of agonist signaling molecul... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 349 | 1,742 | null |
PCR See polymerase chain reaction. PCR product See amplicon. pentose Any simple sugar or monosaccharide containing five carbon atoms. The compounds ribose and deoxyribose are both pentose sugars, which, in the form of cyclic five-membered rings, serve as the central structural components of the ribonucleotides and deox... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 344 | 1,619 | null |
Their domains often undergo rearrangement, dissociation, or conformational changes when they interact with the membrane, resulting in the activation of their biological activity. In protein purification, peripheral membrane proteins are typically more water-soluble and much easier to isolate from the membrane than inte... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 339 | 1,731 | null |
pervasive transcription Petri dish A shallow, transparent plastic or glass dish, usually circular and covered with a lid, which is widely used in biology laboratories to hold solid or liquid growth media for the purpose of culturing cells. They are particularly useful for adherent cultures, where they provide a flat, s... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 332 | 1,587 | null |
phenomic lag A delay in the phenotypic expression of a genetic mutation owing to the time required for the manifestation of changes in the affected biochemical pathways. phenotype The composite of the observable morphological, physiological, and behavioral traits of an organism that result from the expression of the or... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 314 | 1,426 | null |
phosphate Any chemical species or functional group derived from phosphoric acid (H3PO4) by the removal of one or more protons (H+); the completely ionized form, [PO4]3−, consists of a single, central phosphorus atom covalently bonded to four oxygen atoms via three single bonds and one double bond. Phosphates are abunda... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 350 | 1,592 | null |
These bonds are created by ligases and broken by nucleases. phosphodiester bond A pair of ester bonds linking a phosphate molecule with the two pentose rings of consecutive nucleosides on the same strand of a nucleic acid. Each phosphate forms a covalent bond with the 3' carbon of one pentose and the 5' carbon of the a... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 322 | 1,446 | null |
phosphorylation The attachment of a phosphate ion, PO3−4, to another molecule or ion or to a protein by covalent bonding. Phosphorylation and the inverse reaction, dephosphorylation, are essential steps in numerous biochemical pathways, including in the production of adenosine triphosphate (ATP) (as in oxidative phosph... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 317 | 1,364 | null |
plasmid partitioning The process by which plasmids which have been replicated inside a parent cell are distributed equally between daughter cells during cell division. plasmid-mediated resistance The development of resistance to toxins or antibiotics which is enabled by the horizontal transfer of resistance genes encod... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 319 | 1,549 | null |
In microbiology, the ability of some microorganisms such as certain bacteria and viruses to alter their morphology, metabolism, or mode of reproduction in response to changes in their environment. plithotaxis The tendency of cells within a monolayer to migrate in the direction of the local highest tension or maximal pr... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 333 | 1,553 | null |
polyclonal Describing cells, proteins, or molecules descended or derived from more than one clone (i.e. from more than one genome or genetic lineage) or made in response to more than one unique stimulus. Antibodies are often described as polyclonal if they have been produced or raised against multiple distinct antigens... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 305 | 1,550 | null |
polymerase chain reaction (PCR) Any of a wide variety of molecular biology methods involving the rapid production of millions or billions of copies of a specific DNA sequence, allowing scientists to selectively amplify fragments of a very small sample to a quantity large enough to study in detail. In its simplest form,... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 333 | 1,656 | null |
the polymerization of a nucleic acid chain by linking consecutive nucleotides, a reaction catalyzed by a polymerase enzyme. polymorphism polypeptide A long, continuous, and unbranched polymeric chain of amino acid monomers linked by covalent peptide bonds, typically longer than a peptide. Proteins generally consist of ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 345 | 1,525 | null |
polytene chromosome position effect Any effect on the expression or functionality of a gene or sequence that is a consequence of its location or position within a chromosome or other DNA molecule. A sequence's precise location relative to other sequences and structures tends to strongly influence its activity and other... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 313 | 1,679 | null |
This method usually begins by comparing the genomes of individuals expressing a phenotype of unknown provenance (often a hereditary disease) and identifying genetic markers shared between them. Regions defined by markers flanking one or more genes of interest are cloned, and the genes located between the markers can th... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 342 | 1,728 | null |
a unipotent stem cell that is the immediate parent cell from which fully differentiated cell types divide. The term "precursor cell" is sometimes used interchangeably with progenitor cell, though this term may also be considered technically distinct. Pribnow box primary transcript The unprocessed, single-stranded RNA m... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 293 | 1,408 | null |
Natural systems exclusively use RNA primers to initiate DNA replication and transcription, whereas the in vitro syntheses performed in many laboratory techniques such as PCR often use DNA primers. In modern laboratories, primers are carefully designed, often in "forward" and "reverse" pairs, to complement specific and ... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 313 | 1,626 | null |
process molecular gene concept An alternative definition of a gene which emphasizes the contribution of non-DNA factors to the process by which the information encoded in a DNA sequence results in the synthesis of a polypeptide. prometaphase The second stage of cell division in mitosis, following prophase and preceding... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 332 | 1,521 | null |
the decomposition of proteins into smaller polypeptides or individual amino acids, by cleaving peptide bonds via hydrolysis. Proteases are ubiquitous components of numerous biological pathways, and therefore it is often necessary to inhibit them in order for laboratory techniques involving protein activity to be effect... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 330 | 1,785 | null |
polypeptides) synthesized during translation are changed from random coils into stable, orderly, three-dimensional shapes (i.e. proteins) by assuming a higher-order structure or conformation which permits the protein to be biologically functional, known as its native state. Folding is the consequence of polypeptide res... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 327 | 1,746 | null |
Proteins must often be routed into the interior of organelles, embedded within a membrane, or secreted into the extracellular environment in order to serve their functions, and information contained in the protein itself instructs this delivery process. In eukaryotic cells, an expansive network of organelles and pathwa... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 328 | 1,676 | null |
the sum total of all of the proteins produced from it by translation. Proteomics technologies allow scientists to purify and identify proteins and polypeptides and determine which ones are most and least abundant at a given time or under a given experimental condition. proton motive force See chemiosmotic coupling. pro... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 328 | 1,450 | null |
The letter R is sometimes used to indicate a generic purine; e.g. in a nucleotide sequence read, R may be used to indicate that either purine nucleobase, A or G, can be substituted at the indicated position. putative gene A specific nucleotide sequence suspected to be a functional gene based on the identification of it... | Wikipedia - Glossary of cellular and molecular biology (M–Z) - P | 316 | 1,255 | null |
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