Go to Section
A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z
- Saccharomyces cerevisiae (budding yeast)
- [diploid number]
[genome]
- Salmonella
- Ames Test
- Saprophyte
- Heterotrophic plant (or fungus) that secures its food by the extracellular digestion of nonliving organic matter.
- Sarcoma
- A cancer produced by a malignant cell of supporting tissue such as muscle, bone, or cartilage. Compare with carcinoma.
- Sarcomere
- The repeating contractile unit of the myofibril. It is bound on each end by a Z line. [Discussion]
- Scavenger
- Organism that feeds on dead organisms or the wastes of organisms.
- SCID
- Severe combined immunodeficiency [in mice]
- Scion
- Detached part of a plant (e.g., a piece of stem) that is grafted onto another plant.
- Sclerenchyma
- Supporting plant tissue consisting of cells whose walls are uniformly thickened and often lignified. [View]
- Scurvy
- Deficiency disease. [and collagen]
- "Second messengers"
- Second-set graft rejection
- Secondary immune response
- Secondary structure
- [Protein]
- Secretin
- Sedatives
- Seed
- Embryo plant, supplied with food and protected by seed coats, that serves as the agent of dispersal of gymnosperms and angiosperms. It develops from the ovule. [Illustrated discussion]
- Selective serotonin reuptake inhibitors (SSRIs)
- Selector gene
- Gene that regulates the expression of many other genes. Selector genes encode transcription factors.[Examples]
- Sense strand
- The strand of DNA whose 5' -> 3' sequence is the same (substituting T for U) as that of the corresponding mRNA molecule. (Synthesis of this mRNA uses the antisense strand as a template.)
[More]
- Sensitive
- Able to detect a low level of something. The more sensitive the test, the less likely that it will cause "false negatives"; that is, a failure to detect something that is actually present. Compare specific.
- Sequence
- The linear order of amino acids in a polypeptide or nucleotides in a nucleic acid.
- Serine
- [structure]
- Serotonin
- Serum
- The clear fluid that can be squeezed out from a blood clot; hence blood plasma from which the fibrinogen and other clotting factors have been removed. [Discussion]
- Serum sickness
- Severe combined immunodeficiency (SCID)
- [gene therapy for]
- Sex chromosomes
- Chromosomes associated with sex (X and Y in humans). [More]
- Sex hormones
- Sexual reproduction
- The production of new individuals following the mixing in a single cell of the genes of two different cells, usually gametes and usually from different parents.
- Shock
- short gastrulation (sog)
- [role of gene in Drosophila embryology]
- Sickle-cell disease
- [mutation][genetic testing]
- Sievert (Sv)
- [defined]
- Signal sequence
- A short length of amino acid residues found at the amino terminal of those newly synthesized polypeptides destined to enter the endoplasmic reticulum and, often, removed as they do so. [More] [signal recognition particle (SRP)]
- Skeleton
- human
- Skin
- hormones of
- Skin testing
- for immediate hypersensitivities
- small eyes (Sey; also Pax-6)
- mouse gene homologous to eyeless in Drosophila and Aniridia in humans. [More]
- Smell
- the sense of
- Smooth muscle
- [Discussion]
- Snow, John
- [see]
- Sodium/potassium ATPase.
- Solute
- Dissolved substance in a solution.
- Solution
- Mixture consisting of molecules or ions less than 1 nm in diameter suspended in a liquid medium (water in most biological systems). [Schematic of water dissolving crystal of NaCl]
- Solvent
- Dissolving medium of a solution.
- Soma
- [somatic cells]
- Somatostatin
- Somite
- One of the blocks of mesoderm that develop in a longitudinal series on either side of the notochord in vertebrate embryos.
- Sorus
- Speciation
- Formation of species.
- Species
- Taxonomic category consisting of a group of actually or potentially interbreeding natural populations that ordinarily do not interbreed with other such groups even when there is opportunity to do so. (The singular and plural are spelled alike.)
- Specific
- Capable of discriminating between two things. A test that discriminates between infection by the human immunodeficiency virus 1 (HIV-1) and HIV-2 is more specific than one that distinguishes only between infection by any HIV and by the simian immunodeficiency virus (SIV). The more specific a test, the fewer the "false positives";in this example, the less likely that a patient will be diagnosed as HIV-1 positive when he or she is really HIV-2 positive. Some highly specific test and reagents are low in sensitivity and vice versa. Compare sensitive.
- Spemann, Hans
- [egg-tying experiment] [also] [transplant experiment]
- S phase
- [of cell cycle]
- Spinal cord, human
- Spliceosome
- [in pre-mRNA processing]
- Split genes
- [Discussion]
- Sporangium
- Structure within which asexual spores are produced. [in ferns] [in mosses]
- Spore
- Structure, usually unicellular, which serves to disperse the species and/or enable it to survive unfavorable conditions and which can develop into a new individual.
- Sporophyte
- Diploid, spore-producing stage in the life cycle of a plant. [in angiosperms] [in ferns] [in mosses]
- SRY
- Gene on the Y chromosome that determines maleness. [More]
- Stamen
- Starch
- Stem cell
- A cell that gives rise to both differentiated descendants as well as more stem cells. [pluripotent stem cell that produces all the blood cells] [in gene therapy] [in making transgenic mice] [human embryonic stem (ES) cells]
- Steroid
- One of many fat-soluble, biologically active compounds whose molecules contain a system of 4 rings made up of 17 carbon atoms.
-
[cholesterol]
[receptors and response elements] [sex hormones] [progesterone]
- Stigma
- Stimulus
- Anything that initiates a response in a cell or organism.
- Stolon
- Horizontal stem that produces new plants at its nodes.
- Stomach
- [physiology]
- Stomata
- [Discussion] [Hormonal control]
- Striatum
- Structural gene
- A gene encoding a polypeptide.
- Suberin
- Substantia nigra
- Substrate
- (1) Substance that is acted upon by an enzyme. (2) Base (e.g., soil, rock) upon which an organism lives.Also called the substratum.
- Succession
- Progressive change in the nature of the flora of an area.
- Sucrose
- Sugars
- Sulfur dioxide (SO2)
- [acid rain]
- Sulfhydryl group
- [Structure]
- Suspension
- Mixture containing solid particles larger than 100 micrometers distributed throughout a liquid. The particles will eventually settle out under the force of gravity.
- Symbiosis
- The living together in close association of organisms of two different species. Mutualism, commensalism, and parasitism are forms of symbiosis.
- Sympathetic nervous system
- in humans
- Symport pumps.
- Synapse
- Gap between two neurons, or between a motor neuron and an effector (e.g., muscle) cell, into which a neurotransmitter is secreted. [Discussion]
- Synapsis
- Union, side-by-side, of homologous chromosomes early in meiosis.
- Syncytium
- Mass of cytoplasm containing many nuclei. It is formed by the fusion of cells.
- Syndrome
- A collection of symptoms and signs characteristic of a particular disease.
- Synechocystis
- Marine cyanobacterium. [genome]
- Syntenic
- Refers to genes present on the same chromosome. [Examples]
- System
- Group of organs that perform one or more functions as a unit (e.g., the organs of the digestive system).
- Systemic lupus erythematosus (SLE)
- Systole
- Phase of contraction of the heart. [More]