Biology Dictionary – A

Meanings of biological terminology

EUGENE M. MCCARTHY, PHD GENETICS

Definitions:

amygdalitis /ə-mig-də-LĪT-əs/ Inflammation of the tonsils.

amygdaloid /ə-MIG-də-loid/ (1) almond-shaped; (2) pertaining to or resembling a tonsil; (3) a texture of igneous rock in which small cavities initially produced by the expansion of steam in molten lava are subsequently filled with other minerals.

amygdalotome /ah-mig-DALL-ə-tome/ An instrument for excising tonsils.

amylase /AM-ə-laze/ An enzyme, present in saliva, that breaks starch down into sugar.

anabiosis /AN-ə-bī-Ō-səs/ A state of complete dormancy or suspended animation triggered by dessication (for example, in tardigrades) and ended when water is again present — anabiotic /AN-ə-bī-AWT-ick/

anabolic pathways /an-ə-BAWL-ick/ Metabolic processes that consume energy and build up complex molecules from simple ones.

anabolic steroids /an-ə-BAWL-ick/ Hormones promoting constructive, as opposed to catabolic metabolism.

anabolism /ə-NAB-ə-liz-əm/ The production of more complex molecules from simpler ones. Such processes are involved in building up the various molecular constituents of cells and complex tissues from simple compounds ingested by an organism — anabolic /an-ə-BAWL-ick/ See: catabolism

anaerobic /an-ə-RŌ-ick/ adj. Not requiring oxygen to survive. Many anaerobic organisms react negatively, or even die, in the presence of oxygen.

anaerobic respiration /an-ə-RŌ-ick/ See: respiration.

anagenesis /an-ə-JEN-ə-səs/ n. Evolutionary change in a population without branching separation of the population into distinct forms. Compare: cladogenesis.

anal canal /AY-nəl/ The lowermost portion of the large intestine, leading from the rectum to the anus. About 3 cm in length, its aperture is controlled by an internal and external sphincter.

analemma /AN-ə-LEM-ə/ A curve plotting the sun's position through the year as seen from one location at a single time of day.

analogous traits /ə-NAL-ə-gəs/ Traits that are presumed to be similar due to convergence, and not because of their being inherited from a common ancestor.

anaphase /AN-ə-phaze/ (1) The third stage of mitosis (MORE INFORMATION); (2) The third stage of meiosis I (anaphase I) or of meiosis II (anaphase II).

anaphylaxis /an-ə-fə-LACK-səs/ Extreme sensitivity of the body to a particular foreign substance. In a mild anaphylactic reaction, there may be fever accompanied by itching and redness of the skin. Severe cases may involve constriction of the air passages (trachea and bronchi) resulting in dyspnea, cyanosis, unconsciousness, and even death.

anastomosis /ə-NAST-ə-mō-səs/ Reticulate interconnection between blood vessels, or between other organic tubular structures such as the veins of a leaf.

anatomy /ə-NAT-ə-mee/ (1) the macroscopic structure of multicellular organisms; (2) the study of the macroscopic structure of multicellular organisms — anatomist /ə-NAT-ə-mist/

Andrias /AND-dree-əs/ The genus containing the giant salamanders, the largest amphibians known. Two extant forms are recognized, the Japanese Giant Salamander, and the Chinese Giant Salamander. PICTURE2 | PICTURE2

androgen /AND-rə-jen/ A substance that stimulates the production of male characteristics.

anemia /ə-NEEM-ee-yə/ A reduction in circulating erythrocytes, hemoglobin, or both.

anemochore /ə-NEM-ə-kore/ An organism with seeds and/or spores suited to distribution by the wind.

anemometer /AN-em-MOM-ə-tər/ An device used for measuring wind speed.

anencephaly /an-en-SEF-uh-lee/ A serious birth defect in which a child, or the young of any animal, is born without parts of the brain and skull. —anencephalic /an-en-SEF-uh-lik/ More information

anesthesia (British: anaesthesia) /an-es-THEE-zhə/ Loss of sensation.

anesthetic (British: anaesthetic) /an-es-THET-ick/ (1) an agent causing anesthesia; (2) causing anesthesia.

angiorrhaphy /ANJ-ee-ORE-ə-fee/ Suturing of vessels.

angiorrhexis /ANJ-ee-ore-REKS-əs/ Rupture of a blood vessel.

angiosarcoma /ANJ-ee-ō-sar-KŌ-mə/ A sarcoma arising in the cells that line blood or lymph vessels. See: hemangiosarcoma, lymphangiosarcoma.

angiosperms /ANJ-ee-ō-sperms/ Flowering plants; one of the major categories of the Plant Kingdom (Angiospermae /ANJ-ee-ō-SPERM-ee, -ī/ or Magnoliophyta /mag-NŌ-lee-AWF-it-ə/). Unlike gymnosperms, angiosperms form their seeds within protective capsules called ovaries. COMPARISON OF GYMNOSPERM WITH ANGIOSPERM

anisogamy /an-eye-SAWG-ə-mee/ A common type of reproduction in which the two gametes that join to produce the zygote differ greatly in size, with the smaller of the two mobile and seeking out the larger, which is immobile.

ankylodactylia /ank-ə-lō-dak-TILL-ee-ə/ Adhesion of adjacent toes or fingers.

ankylosed /ANG-kə-lōst/ Fused or stiffened (as a joint).

annelid /AN-ə-lid/ A member of phylum Annelida.

Annelida /ə-NEL-id-ə/ A large phylum of segmented worms, including such organisms as the earthworms and leeches.

annotation /an-nō-TAY-shən/ Providing information that describes features of a DNA sequence.

anophthalmia /an-awp-THAL-mee-yə/ Congenital absence of the eyes — anophthalmic /an-awp-THAL-mick/

anorexia nervosa /an-ə-RECK-see-yə nerv-Ō-sə)/ A psychiatric eating disorder characterized by an obsessive fear of gaining weight. Affected individuals are far underweight, but cannot recognize the fact themselves. They intentionally starve themselves to control body weight, and often exercise excessively. Often, too, they take diet pills or diuretics. Most are adolescent females, but about 10 percent are male.

anosomia /ə-NAWZ-mee-yə/ An impairment or lack of the sense of smell.

antepenultimate /an-tee-pen-ULT-ə-mət/ Third from last.

anteriad /an-TIR-ee-ad/ Toward the front.

anterior /an-TIR-ee-er/ In front.

anterolateral /AN-ter-ō-LAT-er-əl/ In front, but toward the side.

anteroposterior /AN-ter-ō-POSS-tir-ee-er/ From front to back.

anther /AN-ther/ The pollen sac at the end of a stamen.

anthracosis /an-thrə-KŌ-səs/ A condition of the lungs caused by chronic inhalation of coal dust.

anthropoid /AN-thrə-poid/ Humanlike; said especially of the great apes (pongids).

anthropomorphism /an-thrope-ə-MORE-fiz-əm/ Interpreting what is nonhuman in terms of what is human; attributing human motives to animals.

antibacterial /ANT-ee-back-TEER-ee-yəl, ANT-ə-/ A substance that kills bacteria or slows their growth.

antibiotic /ANT-ee-buy-AWT-ick, ANT-ə-/ (also antimicrobial /ANT-ee-my-KROBE-ee-yəl, ANT-ə-/) A substance that kills microbes or slows their growth.

antibodies /ANT-ə-bawd-eez/ (also immunoglobulins, abbreviated Ig) Proteins produced by plasma cells in response to foreign substances (antigens). An antibody couples specifically with its antigen (and with molecules sufficiently similar to its antigen). Each plasma cell produces one and only one type of immunoglobulin. MORE INFORMATION

anticipation A situation where successive generations have increased severity of a genetic disorder.

anticoding strand /ANT-ee-KODE-ing/ See: sense strand.

antienzyme /ANT-ee-EN-zime/ Something that neutralizes an enzyme.

antigen /ANT-ə-jen/ A foreign substance that stimulates the production of an antibody.

antigen presenting cell (APC) /ANT-ə-jen/ A cell displaying foreign antigen complex with MHC on its surface. T-cells may recognize this complex using their T-cell receptor (TCR).

antimicrobial See: antibiotic.

antimony (Sb) /ant-ə-MOAN-ee/ n. Chemical element; atomic weight 121.760, atomic number 51. Antimony and many of its compounds are toxic. A lustrous gray, it is intermediate in its properties between a metal and a nonmetal. Symptoms of antimony poisoning are similar to those of arsenic poisoning. PERIODIC TABLE

antisense strand /ANT-ee-sense/ See: coding strand.

antitoxin /AN-tə-TAWK-sən/ See: toxin.

antitussive /AN-tee-TUHS-əv/ n. A cough suppressant (i.e., a cough medicine that acts by suppressing the urge to cough). Dextromethorphan and codeine are the most common antitussives. Compare: expectorant

Anura /an-(Y)ER-ə, ən-(Y)ER-ə/ n. The amphibian order that includes the frogs and toads. Frog calls | PICTURE 1 | PICTURE 2 | PICTURE 3 | DIAGRAM OF FROG LIFE CYCLE —anuran /an-(Y)ER-ən, ən-(Y)ER-ən/ adj.

anus /AY-nəs/ The outlet of the intestinal tract.

aphasia /ə-FAZE-yə/ n. Loss or impairment of the power of speech.

apical /AY-pick-əl/ adj. Occurring at the end or summit.

apical meristems /AY-pick-əl MARE-ə-stems/ Embryonic tissue that supplies cells allowing a plant to grow in length; found at the tips of roots and stems.

Apicomplexa A phylum of protists containing numerous organisms that are important causes of disease, in particular the blood parasites of the apicomplexan genera Babesia, Plasmodium, and Theileria, and the coccidian parasites that infect the intestinal tracts of animals.

apiology /ape-ee-ALL-ə-jee/ The scientific study of bees.

apiphobia /ape-ə-FŌ-bee-ə/ An abnormal, extreme fear of bees.

Apis /APE-əs/ The genus to which the various honey bees, including the common European honey bee, belong. These bees construct colonial nests out of wax.

apnea /AP-nee-ə/ A temporary cessation of breathing.

apocarpous /AP-ə-KARP-əs/ In a gynoecium, having the carpels separate.

apomict /AP-ō-mickt/ An organism that normally reproduces via apomixis.

apomictic /ap-ō-MICK-tic/ Reproducing via apomixis.

apomixis (also apomictic reproduction) /ap-ō-MIX-əs/ Asexual reproduction via agamospermy or vegetative reproduction. MORE INFORMATION

apoptosis /ap-pə(p)-TŌ-səs, ay-/ Programmed cell death. Apoptosis disposes of damaged or unneeded cells.

aposematic /ap-ō-sə-MAT-ick/ Warning, advertising noxious or toxic properties; said of colors, structures, or other features of an organism providing such a warning.

appendectomy /ah-pend-DECT-ə-mee/ Surgical excision of the vermiform appendix.

appendicitis /ə-pend-ə-SĪT-əs/ Inflammation of the vermiform appendix.

approximal /ə-PROKS-ə-məl/ Contiguous.

apterous /AP-tər-əs/ Wingless.

aquatic /ə-KWAT-ək, -ick/ Growing or living in, native to, pertaining to, or taking place in water.

aqueous /AKE-wee-əs/ Of, made of, made by, pertaining to, occurring in, or containing water.

arabinose /ə-RAB-ən-ose, ah-/ A pentose sugar produced by a wide variety of organisms. The L-arabinose operon of E. coli has been extensively studied in molecular genetics.

arachnid /ə-RACK-nid/ A member of the arthropod class Arachnida, which includes ticks, mites, spiders, whip scorpions, whip spiders, scorpions, solpugids, and harvestmen. ABOUT ARACHNID ANATOMY

Archaea /ARK-ee-yə, -eye-yə/ Archaea is one of the two prokaryote domains, the other being Bacteria. PICTURE (Holobacteria) | PICTURE (Korarchaeota) | MORE INFORMATION

archetype /ARK-ə-type/ (1) primitive type; (2) general form or type representing a category. MORE INFORMATION

archocele /ARK-ō-seel, -ə-seel/ Rectal hernia.

argillaceous /are-jə-LAY-shus/ Containing clay.

arginine (Arg or R) /ARJ-ə-neen/ A nonessential amino acid. CODONS | MOLECULAR STRUCTURE

arms (1) the forelimbs of a primate; (2) the locomotive limbs of certain invertebrates, such as the rays of a starfish; (3) the two portions of a chromosome lying on either side of the centromere; the shorter of the two is called the p arm, the longer, the q arm. PICTURE OF HUMAN ARM BONES

arrayed library Individual recombinant clones placed in two-dimensional arrays in microtiter dishes. The clones are hosted in cosmid, bacteriophage, YAC, or other cloning vectors. Each clone in the array is identified by its plate and its location on that plate. Arrayed libraries are used for many purposes, in particular, for screening for a specific gene or genomic region of interest. See also: cloning, genomic library.

arrhenotokous (also arrenotokous) /AR-ə-NAWD-ə-kəs/ Producing male offspring, and only male offspring, from unfertilized eggs.

ARS Autonomously replicating sequence.

arteriogram /are-TEER-ee-ə-gram/ An image produced by arteriography. PICTURE

arteriography /are-teer-ee-AWG-rə-fee/ A method of visualizing the arteries by exposing film to x-rays passed through a patient who has received an injection of a radioopaque solution.

arteriole /are-TEER-ee-əl, -ole/ A minute artery connecting with capillaries.

artery /ARE-ter-ee/ A blood vessel through which blood flows away from the heart. Arteries are of two types, pulmonary, carrying venous blood to the lungs, and systemic, carrying oxygen-enriched blood to the body's tissues. ILLUSTRATION OF ARTERIAL SYSTEM

artiodactyl /ARE-tee-oh-DACK-təl/ n. An even-toed ungulate (as a cow, deer, camel or pig).

arthritis /are-THRĪ-təs/ Inflammation of a joint or joints.

arthrodesis /are-THROW-də-səs or ARE-throw-DEE-səs/ Surgical immobilization of a joint.

arthropod /ARTH-rō-pawd/ An organism belonging to Phylum Arthropoda, which includes all insects, spiders, and crustaceans. An arthropod has jointed appendages and its body is completely covered with an exoskeleton known as a cuticle.

articular /are-TICK-yə-lər/ adj. Of, present in, or pertaining to a joint.

articulate /are-TICK-yə-late/ v. To form a joint.

articulate /are-TICK-yə-lət/ adj. Jointed, having joints.

articulated /are-TICK-yə-lay-təd/ (1) with reference to the individual bones of a fossil skeleton: lying in the same relative position to each other as in life (put together at the joints); (2) in anatomy: having joints; connected by joints.

ascites /ass-ITE-eez/ Accumulation of excess fluid in the abdominal cavity.

ascospore /ASK-ə-spore/ A meiospore within an ascus.

ascus /ASK-əs/ A linear sac produced by ascomycete fungi; it usually contains eight ascospores that are the products of one cell undergoing two meiotic divisions followed by one mitotic division. PICTURE

asexual /ass-EX-yoo-əl/ Lacking separate sexes; in connection with reproduction: occurring without a fusion of gametes. — asexually /ass-EX-yəl-ee/

asn Asparagine.

asp Aspartic acid.

asparagine (A or asn) /ass-PARE-ə-jeen/ A nonessential amino acid. CODONS | MOLECULAR STRUCTURE

asparagine synthase /ass-PARE-ə-jeen SIN-thaze/ An enzyme catalyzing the amination of aspartate to give asparagine. It uses glutamine as a nitrogen source. Aspartate-ammonia ligase is a prokaryotic enzyme that catalyzes the same reaction, but using ammonia as the source of nitrogen. DIAGRAM OF REACTION

aspartate-ammonia ligase /ə-SPART-tate/ See: asparagine synthase.

aspartic acid (D or asp) /ə-SPART-ick/ A nonessential amino acid. CODONS | MOLECULAR STRUCTURE

assembly Assigning short DNA sequences to their correct positions on a chromosome.

assortative mating A tendency of males of a particular type to mate with females of a particular type; "positive assortative mating" occurs when these two types tend to be alike, and "negative assortative mating" occurs when they tend to be different.

assortment The random combination of chromosomes in gametes.

astasia /ə-STAY-zhə/ Incoordination of the muscles while standing erect.

Asteroidea /ass-ter-ROID-ee-yə/ The echinoderm class including the starfishes and sea stars. PICTURE

asthenia /əs-THEEN-ee-yə, ass-/ Weakness, lack or loss of strength, debility.

asthenic /əs-THEN-ick, ass-/ Weak, debilitated.

astrobiology /AST-rə-buy-AWL-ə-jee, AST-rō-/ The study of the possible existence of life in outer space — astrobiologist /AST-rə-buy-AWL-ə-jist, AST-rō-/

ATCase Aspartate carbamoyltransferase.

atelopodia /at-tell-ə-PODE-ee-yə/ Abnormal or incomplete development of the foot.

atelorachidia /at-tell-ə-rah-KID-ee-yə/ Incomplete development of the spine.

atlas /AT-les/ The first (most cranial) vertebra in the spine.

atm Atmosphere; a unit of pressure equal to 101325 Pa.

ATP See: Adenosine triphosphate.

ATPase /AY-tee-pee-aze/ An enzyme that hydrolyzes ATP to ADP and inorganic phosphate.

atrophy /AT-rə-phee/ Shrinkage or disappearance of a part or organ.

attic /AT-ick/ The upper portion of the tympanic cavity.

atticitis /at-ə-SĪT-əs/ Inflammation of the tympanic attic.

attomole /AT-ə-mole/ 10^-18 mole.

audiology /awd-ee-AWL-ə-jee/ The study of hearing and the treatment of its impaired condition.

auricula See: pinna.

auscultation /aw-skəl-TAY-shən/ The process of listening to the sounds of the body, generally of the chest or abdomen, for the purposes of diagnosis and evaluation.

auscultatory /aw-SKUHL-tə-TORE-ee/ Of or relating to auscultation.

australopithecines /AW-strəl-ō-PITH-ə-seens, aw-STRAIL-ō-/ Early hominids discovered in Africa. MORE INFORMATION | HUMAN EVOLUTION TIMELINE

autecic /awt-TEE-sick/ (also autecious /awt-TEE-zhəs/) Pertaining to or being a parasite that, throughout its entire life cycle, infects a single type of host.

autoimmune disease /awt-ō-im-MYOON/ A disease resulting from an attack of the body's immune system on some part of the body itself.

autopolyploid /awt-ō-PAWL-ee-ploid/ A polyploid that is produced without hybridization from a single parental form. Compare: allopolyploid.

autoradiography /awt-ō-raid-ee-AWG-rə-fee/ A technique used in analyzing DNA fragment sizes. Typically radioactive fragments are segregated according to length by allowing them to migrate through an agarose gel subjected to an polarized electrical field (gel electrophoresis). The gel is then placed on X-ray film to visualize the radioactively labeled fragments.

autosomal dominant /awt-ō-SOAM-əl/ A gene that is both dominant and located on an autosome.

autosome /AWT-ə-soam/ A chromosome not involved in sex determination. See: sex chromosome.

autotroph /AWT-ə-trofe, -trawf/ An organism that can produce from an inorganic substrate all of the organic molecules it requires. See: heterotroph.

auxin /AWKS-ən, -in/ A plant hormone with multiple effects. By causing the appropriate cells to lengthen, it brings about secondary growth, and growth toward light (phototrophic response). Also, with gibberellins, it stimulates fruit production.

auxocyte /AWKS-ə-sight/ A spore- or gamete-forming cell during its growth phase.

Avalonia /av-ə-LONE-ee-yə/ A continental plate that bordered the Iapetus Ocean In the Early Paleozoic. It later became part of Euramerica, then part of Pangea, and still later, part of Laurasia. Today, it underlies Nova Scotia, Newfoundland, southern Ireland, and southern England, as well as parts of western Europe and New England.

Aves /AY-veez/ The vertebrate class including all birds.

Avogadro's number /av-ə-GAW-droze/ The number of atoms, 6.022 x 10²³, present in one gram-atomic weight of any element.

av shunt (also a-v shunt) Ateriovenous shunt; a direct connection between an artery and a vein that bypasses the capillary system; may be congenital, caused by trauma, or result from a breakdown in adjacent vessel walls. Arteriovenous shunts are also in some cases created intentionally as part of a surgical procedure.

avuncular relationship /ə-VUHNK-yə-ler/ The genetic relationship that a nephew or niece has to an uncle or aunt.

axial /AX-ee-yəl/ (1) pertaining to an axis; (2) around an axis; (3) along or parallel to an axis.

axon /AX-on/ A neuron process that carries nerve impulses away from the cell.

azurophil /azh-YER-ə-fil/ (also azurophile /azh-YER-ə-file/) A tissue, microorganism, or a part of a microorganism with an affinity for blue (azure) dye such as the commonly used azure B.

azymic /az-ZĪM-ick/ (also azymous /az-ZĪM-məs/) Unfermented, unleavened.

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