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A
- ABC model of the control of flowering
- abl
- [gene]
- ABP1
- Auxin-binding protein 1
- Abscisic acid (ABA)
- Plant hormone.
- Abscission
- Absorption spectrum
- Electromagnetic spectrum whose intensity at each wavelength is a measure of the amount of energy at that wavelength that has passed through a selectively absorbing substance.
- Acetylcholine
- Substance secreted at the ends of many neurons. A neurotransmitter. [More] [At neuromuscular junction]
- Acid
- Molecule or ion that liberates protons, usually in water. [Discussion]
- Acid rain
- Rain more acid than normal (below pH 5.6). [More]
- ACTH
- adrenocorticotropic hormone
- Actin filaments
- [Discussion] [in cytokinesis] [in skeletal muscle]
- Action potential
- Action spectrum
- Rate of physiological activity plotted against wavelength of light.
- Active transport
- Transfer of a molecule or ion across a cell membrane against its concentration gradient. Requires energy. [Discussion]
- Activins
- [in embryonic development] [sex hormones]
- Acute lymphoblastic leukemia (ALL)
- [More]
- Acute myelogenous leukemia (AML)
- Adaptation
- Any characteristic of an organism that contributes to its survival in its environment.
- Adaptive radiation
- Evolution, from a single ancestral species, of a variety of descendant species adapted to different ways of life.
- Adeno-associated virus (AAV).
- As vector for somatic gene therapy.
- Addison's disease
- Adenine
- [structure]
- Adenosine deaminase (ADA)
- and severe combined immunodeficiency (SCID)
- Adenylyl cyclase
- [and peptide hormones] [and odorant receptors]
- ADH
- antidiuretic hormone
- Adherens junctions
- Adhesion
- Force of attraction between unlike molecules.
- Adipose tissue
- Fat. [More] [secretion of leptin by]
- Adrenal glands
- [Hormones of]
- Adrenaline
- Hormone produced by the adrenal glands that mobilizes the body to meet sudden stress. In the U.S., it is often called epinephrine. Adrenalin (without the e) is a trade name. [More]
- Adrenocorticotropic hormone
- ACTH
- Adventitious root
- Root that arises from a stem or leaf.
- Aerobic
- Requiring the presence of free oxygen.
- AGAMOUS (AG)
- Agent Orange
- Mixture of herbicides sprayed by the U.S. military in VietNam.
[More] [dioxin content]
- Agonist
- Drug that mimics the action of another.[Example]
- AIDS
- Acquired immunodeficiency syndrome. [and CD4 T cells] [HIV-1] [role of apoptosis]
- Alanine
- One of the 20 amino acids used in the synthesis of proteins. [Structure]
- Aldosterone
- Alga
- A photosynthetic eukaryote generally found in damp or aquatic locations.
- ALH84001
- Martian meteorite. [More]
- Alkylation
- Addition of a carbon-containing group, such as a methyl or ethyl group, to another molecule.
- Allantois
- Allele
- Alternative version of a gene.
- Allergen
- An antigen that provokes an allergic response.
- Allergy
- An exaggerated response to a normally harmless material; a hypersensitivity. [Discussion]
- Allograft
- Graft of tissue between genetically different members of the same species. [More]
- Allopatric
- Refers to populations living in separate, usually adjacent, geographic areas. If gene flow between adjacent populations is sufficiently low, they may evolve into separate races (= subspecies) and, ultimately, into separate species.
- Allosteric
- Refers to a change in the properties (usually including shape) of a protein following the binding of another molecule to the protein. [Example]
- Allozyme
- Allelic version of an enzyme. Heterozygotes synthesize both versions of the enzyme, which often can be distinguished by their different rates of migration during electrophoresis. If the enzyme is a homodimer, heterozygotes will synthesize three versions: AA, Aa, and aa.
- Alpha helix
- [in proteins]
- Alternation of generations
- [Discussion] [in ferns] [in mosses]
- Alu sequence
- One type of repetitive DNA consisting of a sequence of about 300 base pairs with some 300,000 copies in the human genome. The sequence is recognized by the restriction enzyme AluI.
- Aluminum
- Metallic element (Al). [More]
- Ames Test
- In vitro test for determining if a chemical is a mutagen. [More]
- Amino acid
- Monomer used in the assembly of proteins. [More]
- Aminoglycosides
- Aminopeptidase
- Amino terminal
- The end of a polypeptide with a free amino group. Synthesis of polypeptides proceeds from the amino terminal to the carboxyl terminal.
[view]
- AML
- acute myelogenous leukemia
- Ammonium ion
- Amniocentesis
- Removal of amniotic fluid from a pregnant woman in order to study its composition and/or culture the fetal cells contained in it.
- Amnion
- Amniota
- All the vertebrates whose embryo is enveloped in an amnion: reptiles, birds, and mammals. [More]
- AMPA receptors
- Amphetamine
- A drug that is similar in molecular structure to adrenaline and noradrenaline and shares their stimulatory properties. [Discussion]
- Amphiphilic
- Used to describe molecules containing both polar (hydrophilic) and apolar (hydrophobic) groups. Sodium stearate (a soap) is amphiphilic.
- amygdala
- Amylase
- An enzyme that digests (hydrolyzes) starch. [pancreatic amylase]
- Amylopectin
- Amylose
- Anabolic steroid
- One of a number of synthetic steroids that, among other effects, seem to promote anabolism and hence an increase in body weight. They are all close relatives of the androgen, testosterone. [More]
- Anabolism
- Constructive metabolism in which complex substances are synthesized from simpler ones. [ More ]
- Anaerobic
- Not requiring the presence of free oxygen.
- Analogous
- Of structures (e.g., molecules, organs) in different species having similar function(s) but inherited from different precursors.
- Anaphase
- [mitosis][meiosis]
- Anaphase Promoting Complex (APC)
- in cell cycle
- Anaphylaxis
- [local] [systemic]
- Androgen
- One of a group of steroids in male vertebrates that promotes the development of their secondary sex characteristics. Testosterone is an example.
- Anemia
- Deficiency of red blood cells or hemoglobin in the blood. [More] [pernicious] [immune hemolytic]
- Anesthetic
- A substance that produces loss of sensation. [More]
- Aneuploid
- Having one or more extra (or fewer) chromosomes than the normal diploid (2n) set (e.g., 2n+1, 2n-1). [trisomy 21] [X chromosomes]
- Angelman syndrome
- An inherited disorder of genomic imprinting. [More]
- Angiosperms
- The flowering plants. [Discussion].
- Angiostatin
- Angiotensin
- Angstrom (Å)
- [defined]
- Aniridia
- [human gene]
- Antenna pigments
- [in photosynthesis]
- Antennapedia (Antp)
- Drosophila selector gene.[see encoded homeodomain]
- Anther
- Antheridia
- [in ferns] [in mosses]
- Antibiotics
- [discussion]
- Antibody
- A protein that unites specifically with a particular antigen.
- [Structures] [3D view]
- Anticodon
- The group of 3 adjacent nucleotides on a transfer RNA (tRNA) molecule that pairs with a complementary codon on a messenger RNA (mRNA) molecule. [More]
- Antidepressant drugs
- Antidiuretic hormone
- ADH
- Antigen
- Macromolecule (usually a protein or polysaccharide) which, when introduced into the body of a vertebrate to which it is foreign, stimulates the formation of antibodies and/or of immune T cells. [Receptors on B and T cells][presentation to T lymphocytes]
- Antigenic determinant
- A part of an antigen to which the antibody binds. Also called an epitope.
- Antigenic drift
- of influenza viruses
- Antiport pump.
- Antisense strand
- The strand of DNA used as the template for synthesizing RNA.
[More] [Antisense oligodeoxynucleotides (ODNs)] [Antisense RNA]
- Antiserum
- Serum containing induced antibodies.
- Antithymocyte globulin (ATG)
- Antitoxin
- Mixture of antibodies formed in response to injections of a toxin or toxoid.
- APETALA
- Apical dominance
- Apomixis
- Reproduction by seeds that have developed asexually rather than sexually.
- Apoptosis
- Programmed cell death. [Discussion]
- Aquaporin
- Aqueous humor
- of human eye
- Aquifer
- A layer in the earth that is saturated with water.
- Arabidopsis thaliana
- [diploid number]
[genome size]
- Arachidonic acid
- Archaea
- Third kingdom of life. example: Methanococcus jannaschii
- Archegonia
- [in ferns] [in mosses]
- Archenteron
- Central cavity of the gastrula of an embryo which eventually becomes the alimentary canal. [view]
- ARF1
- Auxin response factor 1
- Arginine
- [structure]
- Arteriosclerosis
- Arthropod
- A member of the phylum of invertebrate animals characterized by jointed legs and exoskeleton. Includes insects, arachnids, and crustaceans.
- Ascorbic acid
- vitamin C
- Ascus
- Tubular spore sac of ascomycetes in which eight (usually) ascospores are produced.
- Asexual reproduction
- Formation of a new individual from the cell(s) of a single parent.
- Asparagine
- [structure]
- Aspartic acid
- [structure]
- Assortative mating
- Mating between similar individuals; therefore a form of nonrandom mating.
- Asthma
- Discussion
- Atherosclerosis
- [More] [and cholesterol]
- Atom
- Smallest particle of an element that can combine with other elements. [More]
- Atomic number
- Atomic weight unit
- One-twelfth the weight of an atom of carbon-12. Also called the dalton. [More]
- Atopy
- ATP (adenosine triphosphate)
- [structure][yield in cellular respiration]
- ATP synthase
- [in photosynthesis][in mitochondria]
- Atrial natriuretic peptide
- ANP
- Autocrine
- Refers to the influence on a cell of molecules synthesized by the same cell. [More]
- Autoimmune disease
- Disease characterized by the mounting of an immune response against constituents of an individual's own tissues. Some examples: [Insulin dependent diabetes mellitus (IDDM)] [Immune hemolytic anemia] [Immune thrombocytopenic purpura] [Myasthenia gravis (MG)] [Multiple sclerosis (MS)] [Rheumatoid arthritis] [Systemic lupus erythematosus (SLE)] [Thyrotoxicosis (Graves' disease)]
- Autonomic nervous system
- in humans
- Autosome
- Any chromosome that is not a sex chromosome.
- Autotrophic
- Capable of synthesizing organic molecules from inorganic raw materials.[Photosynthesis]
- Auxin
- Plant hormone that, among other effects, promotes cell elongation. [Discussion]
[Auxin-binding protein 1 (ABP1)] [Auxin response factor 1 (ARF1)]
Several herbicides (2,4-D for example) have molecular structures similar to auxin.
- Avogadro's number
- Axon
- Single extension of a neuron (usually long and often branched) which conducts nerve impulses (action potentials) away from the dendrites or cell body.
- Azathioprine
- Purine analog used as an immunosuppressant.
- AZT
- Azidodeoxythymidine. Drug used to treat HIV infection. Has no 3' OH, thus terminating DNA synthesis by reverse transcriptase. Also called zidovudine. [Structure]