packaging cell lineA cell line designed to produce viral particles that do not contain nucleic acid.
packed cell volume(Abbreviation: PCV). The proportion of a cell culture volume that is occupied by cells.
PAGEA single image of the equivalent of one piece of paper. One or several pages make up a Document.
pair-rule geneA gene that influences the formation of body segments in Drosophila.
pairingThe pairing of homologous chromosomes during the prophase of the first meiotic division.
palaeontologyThe study of the fossil record of past geological periods and of the phylogenetic relationships between extinct and contemporary plant and animal species.
PaleontologyThe study of the fossil record of past geo- logical periods and of the phylogenetic relationships between ancient and contemporary plant and animal…
Palindromic sequenceA DNA locus whose 5'-to-3' sequence is identical on each DNA strand. The sequence is the same when one strand is read left to right and the other strand…
palisade parenchymaElongated cells found just beneath the upper epidermis of leaves, typically rich in chloroplasts.
pAMPAmpicillin-resistant plasmid developed for this laboratory course. (See Plasmid.)
panicleAn inflorescence, the main axis of which is branched; the branches bear loose racemose flower clusters.
panicle cultureAseptic culture of immature panicle explants to induce microspore germination and development.
PARPerformance and Accountability Report -- see Annual Reports for more
par geneOne of a class of genes required for faithful plasmid segregation at cell division.
paracentric inversionA chromosomal rearrangement in which a segment of chromosome, excluding the centromere, is rotated.
paraffin [wax]A translucent, white, solid hydrocarbon with a low melting point. One use is as an embedding medium to support tissue for sectioning for light microscopy…
ParafilmäA stretchable film based on paraffin wax; used to seal tubes and Petri dishes. Parafilmä is a proprietary name which is incorrectly applied colloquially…
parahormoneA substance with hormone-like properties that is not a secretory product (e.g. ethylene; carbon dioxide).
parallel evolutionThe development of different organisms along similar evolutionary paths due to similar selection pressures acting on them.
paralogousHomologous genes/gene products that have duplicated and evolved divergently within a species. e.g. beta- and gamma-globulin genes
parameterA value or measurement that varies with circumstances, and is used as a reference to quantify a situation or a process.
parasexual cycleA sexual cycle involving changes in chromosome number but differing in time and place from the usual sexual cycle; occurring in those fungi in which the…
parasiteAn animal or plant that gets nutrients by living on or in an organism of another species.
ParasitismThe closee association of two or more dissimilar organisms where the association is harmful to at least one. See Commensalism, Parasitism, Symbiosis.
parasporal crystalTightly packaged insect pro-toxin molecules that are produced by strains of Bacillus thuringiensis during the formation of resting spores.
parthenocarpyThe development of fruit without fertilization.
ParthenogenesisProduction of an embryo from an unfertilized egg.
partial digestIncomplete reaction of a restriction enzyme with DNA, such that only a proportion of the target sites are cleaved.
particle radiationHigh energy nuclear emissions, used as physical agents of mutagenesis. Three major types typically used: alpha (☐) (positively charged), beta (☐)…
parts per million(Abbreviation: ppm). Unit of concentration: 1ppm = 1mg dissolved matter per litre of solution.
PassageThe transfer or transplantation of cells from one culture medium to another.
passage numberThe number of times cells in culture have been sub-cultured.
passage timeTime interval between successive sub-cultures.
passive immunity1. Natural acquisition of antibodies by the foetus or neonate (newborn) from the mother. 2.
pat geneA gene obtained from Streptomyces sp. encoding resistance to glufosinate-ammonium containing herbicides. (These inhibit plant synthesis of glutamine).
patentA grant to an inventor of the right to exclude others, for a limited time, from making, using, or selling his invention in the United States.
pathogenesis related protein(Abbreviation: PR protein ). One of a group of proteins that are characteristically highly expressed as part of a plant's response to pathogen attack.
pathotoxinSubstance secreted by certain pathogens, in order to attack the host tissue. Some pathotoxins are also toxic to non-hosts, especially animals or humans.
pathovarStrain of a plant-attacking bacterium or fungus that can be differentiated from others by their interaction with specific s.
pectinA group of naturally occurring complex polysaccharides, containing galacturonic acid, found in plant cell wall s, where their function is to cement cells…
pectinaseEnzyme catalysing the hydrolysis of pectin. Used in conjunction with cellulase to solubilize plant cell walls.
pedicelStalk or stem of the individual flowers of an inflorescence.
pedigreeA record of one's ancestors, offspring, siblings, and their offspring that may be used to determine the pattern of certain genes or disease inheritance…
peduncleStalk or stem of a flower that is born singly; the main stem of an inflorescence.
PenetranceThe proportion of individuals in a population that express the phenotype expected from their genotype with respect to a specific gene.
peptidaseAn enzyme that catalyzes the hydrolysis of a peptide bond.
peptideAny compound consisting of two or more amino acids, the building blocks of proteins.
peptide bondThe chemical bond holding amino acid residues together in peptides and proteins.
peptide expression libraryA collection of peptide molecules, produced by recombinant cells, in which the amino acid sequences are varied.
peptide nucleic acid(Abbreviation: PNA). A synthetic oligonucleotide analogue, in which the sugar backbone is replaced by a peptide chain, upon which the nucleoside residues…
peptide vaccineA short chain of amino acids that can induce antibodies against a specific infectious agent.
peptidyl transferaseAn enzyme bound tightly to the large sub-unit of the ribosome, that catalyses the formation of peptide bonds between amino acids during translation.
peptidyl-tRNA binding site(Abbreviation: P-site). The site on a ribosome that hosts the tRNA to which the next amino acid for the growing polypeptide chain is attached.
perennialA plant that flowers continuously for several years.
pericentric inversionA chromosomal rearrangement in which a segment of chromosome, including the centromere, is rotated.
periclinalThe orientation of cell wall or plane of cell division parallel to the reference surface.
periclinal chimera1. Genotypically or cytoplasmically different tissues arranged in concentric layers. 2.
pericycleRegion of the plant bounded externally by the endodermis and internally by the phloem. Most roots originate from the pericycle.
periplasmThe space between the cell (cytoplasmic) membrane of a bacterium or fungus and the outer membrane or cell wall. Synonym: periplasmic space.
permanent wilting point(Abbreviation: PWP). The moisture content of a soil below which plants wilt to such an extent that they fail to recover even when fully watered.
PermeableReferring to a membrane, cell or cell system through which small molecules can diffuse.
persistenceAbility of an organism to remain in a particular setting for a period of time after it is introduced.
PersistentChemicals with a long inactivation or degradation time, such as some pesticides.
PERVAbbreviation for porcine endogenous retrovirus.
Pesticide(PES-tih-side) Any substance that is used to kill insects and other pests.
Pesticide resistanceA genetic change in response to selection by a pesticide, resulting in the development of strains capable of surviving a dose lethal to most individuals…
petalOne of the parts of the flower that make up the corolla.
Petri dishFlat round glass or plastic dish with a matching lid, used for small-scale culturing of organisms, germinating seeds etc.
PFGEAbbreviation for pulsed-field gel electrophoresis.
PGOne of several hormone-like substances made by the body. Different PGs control blood pressure, contraction of smooth muscles, and other processes within…
pHA measurement for liquids to determine acidity or alkalinity. On a scale of one to 14, seven is considered neutral.
pH-electrode-based sensorSensor in which a standard pH electrode is coated with a biological material. Many biological processes raise or lower pH, and the changes can be detected…