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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
- Rad
- [defined]
- Radiation
- [ionizing] [and cancer] [spectrum of electromagnetic radiation]
- Radicle
- Root portion of the embryo of seed plants. [View]
- Random assortment
- [of chromosomes in meiosis]
- Rapamycin
- Immunosuppressant drug. [as regulator of transgene expression]
- RB
- Retinoblastoma gene
- Reactant
- Substance that enters into a chemical reaction.
- Recapitulation
- Occurrence, in embryonic development, of stages thought to have occurred in the embryonic development of its ancestors.
- Recognition helix
- Recombinant DNA
- Discussion
- Recommended dietary allowances (RDAs)
- [table with 1997 revisions (Dietary Reference Intakes)]
- Redox potential
- A measure (in volts) of the affinity of a substance for electrons compared with hydrogen (which is set at 0). Substances more strongly electronegative than (i.e., capable of oxidizing) hydrogen have positive redox potentials. Substances less electronegative than (i.e., capable of reducing) hydrogen have negative redox potentials.[in photosynthesis]
- Redox reaction
- A chemical reaction in which electrons are transferred from one atom (which is thereby oxidized) to another (which is thereby reduced).
- Reduction
- Process of adding electrons to a substance.
- Refractory period
- Brief interval following the propagation of an action potential in a neuron or muscle fiber during which it is incapable of propagating a second action potential. [in neurons] [in muscle fibers]
- Regulator gene
- A gene that encodes a transcription factor and thus controls the expression of other genes.
- Relaxin
- Releaser
- Stimulus that initiates instinctive behavior.
- REM
- Roentgen equivalent man. The amount of absorbed radiation that will cause as much damage in human tissue as 1 roentgen of x rays. [More]
- Renin
- Kidney hormone
- Replication origin
- [DNA]
- Reporter genes
- Repressor
- A protein that blocks gene transcription by combining with its operator. [lac repressor] [tryptophan repressor]
- Respiratory chain
- [in mitochondria]
- Response element (RE)
- A particular DNA sequence which, when bound by a protein specific for it, turns its associated gene(s) on (or off). Many response elements bind to a complex of a hormone with its protein receptor. [steroid response elements] [response element of a protein hormone]
- Resting potential
- Restriction endonuclease
- An enzyme that cuts DNA molecules only at one or close to certain sequences of nucleotides.[Discussion]
- Restriction fragment length polymorphism (RFLP)
- Variations (seen in different members of a species) in the length of a DNA fragment produced by digestion with a particular restriction endonuclease. RFLPs are inherited as typical Mendelian traits. [Discussion]
- Reticular formation
- Retina
- of human eye
- Retinoblastoma
- Discussion
- Retinal
- Prosthetic group of the visual pigments of the eye [More]
- Retinol
- vitamin A
- Retrovirus
- A virus whose genome consists of RNA which, after infection, is copied by reverse transcriptase into DNA. The human immunodeficiency viruses (HIV) are retroviruses. [life cycle] [as vector in gene therapy]
- Reverse transcriptase
- An enzyme that catalyzes the synthesis of DNA that is complementary to an RNA template; that is, an RNA-dependent DNA polymerase. [More]
- Rh disease
- Hemolytic disease of the newborn
- Rheumatoid arthritis
- as autoimmune disease
- Rhizobia
- Soil bacteria of the genus Rhizobium which are able to fix nitrogen after establishing a symbiotic relationship with the roots of a legume.
- Rhizoid
- Hairlike structure that serves as a root for bryophytes, fern prothallia, and certain fungi and lichens.
- Rhizome
- Underground stem.
- Riboflavin
- vitamin B12
- Ribonucleic acid (see RNA)
- Ribonucleoprotein
- A complex of RNA and protein.
- Ribose
- [structure]
- Ribosome
- [in protein synthesis]
- Ribulose bisphosphate carboxylase oxygenase (RUBISCO)
- [in photosynthesis] [genes]
- Rickets
- Rifampin
- Risk
- [relative]
- RNA
- Ribonucleic acid. A polymer of
ribonucleotides. Performs various functions in the synthesis of proteins. [types] [processing] [small nuclear (snRNA)] [Antisense RNA]
- Ritalin
- Rituximab
- RNA polymerase
- An enzyme that catalyzes the polymerization of ribonucleotides to form RNA complementary to a template (either DNA or RNA).[types in eukaryotes]
- Rods
- of human retina
- Rough endoplasmic reticulum (RER)
- [and protein synthesis]
- RUBISCO
- see Ribulose bisphosphate carboxylase oxygenase
- RU-486
- A progesterone antagonist used to prevent or terminate pregnancy. Also called mifepristone. [More] [still more]