sub-cultureDivision and transfer of a portion of a culture to fresh medium. Sometimes used to denote the adding of fresh liquid to a suspension culture.
sub-culture numberThe number of times cells, etc., have been sub-cultured..
sub-strainDerived from a strain by the isolation of an individual or group of individuals having properties or markers not shared by the strain as a whole.
sub-unit vaccineOne or more immunogenic protein s, either purified from the pathogen itself or produced from a cloned pathogen gene.
SubcloningThe process of tranferring a cloned DNA fragment from one vector to another. (See Cloning.)
SubculturingTransferring cultured cells, with or without dilution, from one culture vessel to another.
subgenomic promoterA promoter added to a virus for a specific heterologous gene, resulting in the formation of mRNA for that gene alone.
subspeciesPopulation(s) of organisms sharing certain characteristics that are not present in other populations of the same species.
substitutionReplacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one amino acid in a protein by another amino acid.
Substrate1. A compound that is altered by an enzyme. 2. Food source for growing cells or micro-organisms. 3. Material on which a sedentary organism lives and grows.
Subunit vaccineA vaccine composed of a purified antigenic determinant that is separated from the virulent organism. (See Vaccine, Enzyme.)
suckerA shoot that arises from an underground root or stem. Of particular significance to grafted plants, since the sucker will be genotypically rootstock…
suckeringType of vegetative propagation where lateral buds grow out to produce an individual that is a clone of the parent.
suicide geneA strategy for making cancer cells more vulnerable to chemotherapy. One approach has been to link parts of genes expressed in cancer cells to other genes…
Sulfated proteoglycanMolecules found primarily in connective tissues and joint fluids and that provide lubrication.
superbugJargon for a particular engineered strain of Pseudomonas, in which various hydrocarbon-degrading genes, derived from different plasmids, were combined…
supercoilThe conformation of a double-stranded DNA molecule placed under torsional stress as a result of interactions with protein s.
Supercoiled plasmidThe predominant in vivo form of plasmid, in which the plasmid is coiled around histone-like proteins.
SupergeneA group of neighboring genes on a chromosome that tend to be inherited together and sometimes are functionally related.
SupernatantThe soluble liquid &action of a sample after centrifugation or precipitation of insoluble solids.
Suppressor geneA gene that can suppress the action of another gene.
suppressor mutationA mutation that reverses the effect of an earlier mutation, e.g. a mutation in a gene for a tRNA that permits it to read and override an amber mutation.
suppressor-sensitive mutantAn organism that can grow in the presence, but not in the absence of a second genetic factor (the suppressor).
Surface markerSurface proteins that are unique to certain cell types capable of detection by antibodies or other detection methods.
Surface markersProteins on the outside surface of a cell that are unique to certain cell types, which are visualized using antibodies or other detection methods.
susceptibleInability to withstand injury due to biotic or. Opposite: resistance, tolerance.
suspension cultureA type of culture in which cells and/or clumps of cells grow and multiply while suspended in a liquid medium.
symbiontAn organism living in symbiosis with another, dissimilar organism.
SymbiosisThe close association of two or more dissimilar organisms where both receive an advantage from the association. See Commensalism, Parasitism.
sympatric speciationThe evolution of new species by population s that inhabit the same or overlapping geographic regions.
sympodialA type of plant development in which the terminal bud of the stem stops growing due either to its abortion, or to its differentiation into a floral…
SynapsisThe pairing of homologous chromosome pairs during prophase of the first meiotic division, when crossing over occurs.
synaptonemal complex(Abbreviation: SC). A ribbon-like protein aceous structure formed between paired homologous chromosome s at the end of the first meiotic prophase.
synchronous cultureA culture in which the cell cycle is synchronized for the majority of the cells present.
SyncytiotrophoblastA multinucleated cell formed from the cells of the trophoblast. Only a small area of the syncytiotrophoblast is evident at the start of the formation of…
syncytiumA large cell-like structure formed by the joining together of two or more cells. The plural is syncytia.
syndrome(SIN-drome) A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the…
synergidOne of the two haploid nuclei at the micropylar end of the embryo sac of higher plants. The third nucleus is the egg.
synergismAn interaction between two organisms (e.g. Rhizobium and legumes) in which the growth of one is helped by the other. Opposite: antagonism.