S

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.) [View] The sense strand is sometimes called the Crick strand.

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.

Sensitization

Separins

Sepsis

Sequence: The linear order of amino acids in a polypeptide or nucleotides in a nucleic acid.

Serine

Serine proteases

Serotonin: also known as 5-hydroxytryptamine (5HT) [receptors] [serotonin reuptake inhibitors (SRIs)]

Serpins

Serum

Serum sickness

Severe combined immunodeficiency (SCID): [X-linked SCID] [adenosine deaminase deficiency] [defective V(D)J recombination] [in mice]

Sevin

Sewage Treatment

Sex chromosomes

Sex determination: [in honeybees] [environmental]

Sex hormones

Sex organs: [of human female] [of human male]

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. [in humans] [in angiosperms] [in gymnosperms] [in mosses] [in ferns] [in bacteria] [in Paramecium]

Sexual selection

Sey ("small eyes") gene

Shade avoidance effect

Shock

Sickle-cell disease

Sievert (Sv)

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)]

Silencers

Silver Springs ecosystem

SINES (Short Interspersed Elements)

Single nucleotide polymorphisms (SNPs)

Sino-atrial (S-A) node

Sips equation

Sir2 gene

SIV (Simian Immunodeficiency Virus)

Skeleton, human

Skin: hormones of

Skin testing: for immediate hypersensitivities

SLG (S-Locus Glycoprotein)

Slime molds: [cellular] [plasmodial (Myxomycetes)]

SMADs

small eyes (Sey; also Pax6): mouse gene homologous to eyeless in Drosophila and Aniridia in humans. [More]

Smallpox

Smell, the sense of

Smog, photochemical

Smooth muscle

SNAREs

Snow, John

Sodium/potassium ATPase.

sog ("short gastrulation") gene

Soil

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)

Somatic-cell nuclear transfer (SCNT)

Somatic hypermutation (SHM)

Somatostatin

Somite: One of the blocks of mesoderm that develop in a longitudinal series on either side of the notochord in vertebrate embryos.

Sorus

Southern blot

Speciation

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.) [More]

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 tests and reagents are low in sensitivity and vice versa. Compare sensitive.

Specificity, antibody

Spemann, Hans: [egg-tying experiments] [the organizer] [and eye induction]

Spermatogenesis

S phase of cell cycle

Sphenopsids

Spinal cord, human

Spindle checkpoint

Spiracles, insect

Spirochetes

Spliceosomes: [in pre-mRNA processing] [contain a ribozyme]

Sponges (Porifera)

Sporangium: Structure within which asexual spores are produced. [in ferns] [in mosses] [in slime molds]

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]

Sporozoans

Squid, hearts of

SRC gene

SRK (S-Receptor Kinase)

SRY: Gene on the Y chromosome that determines maleness. [More]

Stahl, F. W.

Stamen

Standard: [deviation] [error of the mean (S.E.M.)]

Staphylococci

Starch

Stele

Stem cell: A cell that gives rise to both differentiated descendants as well as more stem cells. [general discussion with links to other pages]

Stems, plant

Stereocilia

Sterile-male technique

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] [adrenal hormones]

Sticklebacks: [evidence of sympatric speciation] [mating behavior] [Pitx1 gene]

Stigma

Stimulus: Anything that initiates a response in a cell or organism.

Stolon

Stomach: [physiology]

Stomata: [Discussion] [hormonal control]

STR (Short Tandem Repeat)

Streptococci

Streptococcus pneumoniae: [rough and smooth] [types] [genome]

Striatum

Strigolactones

Stroma, of chloroplast

Suberin

Subspecies (races)

Substance P

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.

Subtilisin

Succession, plant

Sucrose

Sugars

Sulfhydryl group

Sulfur dioxide (SO₂) and acid rain

Superoxide anion

Superoxide dismutase (SOD)

Suprachiasmatic nuclei (SCN)

Sup35p

Survivorship curves

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

Sympathetic nervous system, in humans

Sympatric speciation

Symplast

Symport pumps.

Synapses: [in nervous system] [electrical] [immunological]

Synapsida

Synapsis: Union, side-by-side, of homologous chromosomes early in meiosis I.

Synaptonemal complex (SC)

Syncytium: Mass of cytoplasm containing many nuclei. It can be formed by the fusion of cells (e.g., skeletal muscle fibers) or by the repeated mitosis of nuclei without accompanying cytokinesis (e.g., insect blastula).

Syndecan-1

Syndrome: A collection of symptoms and signs characteristic of a particular disease.

Syntenic: Refers to genes present on the same chromosome. [Examples]

Syphilis

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

Next Search

Welcome