Online Biology Dictionary - C

C (1) cytosine; (2) cysteine; (3) carbon; (4) Celsius; (5) clonus; (6) centum (100); (7) cum (Latin: with); (7) centigrade.

C¹⁴ The radioactive isotope of carbon.

Є Cambrian.

Ca Calcium.

caconym /KAK-uh-nim/ A taxonomic name considered bad for linquistic reasons.

Caenorhaditis elegans (click to enlarge)

Caenorhaditis elegans
/see-no-rab-DIGHT-uhs EL-uh-guhns/ A nematode much used in biological research, particularly in the field of developmental genetics. Because it is transparent, every cell in its body can be seen. Adults have just 816 cells (302 are neurons). The fate of every cell at every stage of development is known.

calcaneus /kal-KANE-ee-uhs/ A bone of the tarsus, which in human beings underlies the heel; the heel bone. INFERIOR SURFACE | SUPERIOR SURFACE | LATERAL SURFACE | MEDIAL SURFACE

cal Calorie.

calcareous /kal-KARE-ee-uhs/ Containing, or composed of, calcium carbonate.

calcite /KAL-sight/ A form of calcium carbonate.

calcitonin /KAL-suh-TONE-uhn/ A 32-amino acid linear polypeptide hormone secreted by the thyroid gland which acts to reduce blood calcium levels; found in a broad range of vertebrates.

calcium (Ca) /KAl-see-uhm/ Silver-white metallic element. Atomic weight 40.08; atomic number 20. Vertebrates require relatively large amounts of calcium for the production and maintenance of bone. It is also essential to the function of nerves and muscles. Parathyroid hormone increases blood calcium levels, and the thyroid hormone calcitonin reduces it

calcium carbonate /KAl-see-uhm CARB-uh-nate/ A white compound (CaCO₃) occurring naturally as chalk, limestone, and marble. Many invertebrates, such as mollusks, corals, and echinoderms construct their exoskeletons from calcium carbonate. Seashells are composed of calcium carbonate. It also is present in the tests of many microorganisms. All vertebrate eggs laid on land (amniotic eggs), except turtle eggs, have shells made of calcite, a form of calcium carbonate. Turtles lay eggs made of aragonite, another form of calcium carbonate.

calcium phosphate /KAl-see-uhm FOSS-fate/ A compound making up 85 percent of the mineral content of bone. It also makes up three-quarters of the ash remaining after cremation.

Calico Cat Credit: Rehman Abubakr

calico cat (British: tortoiseshell-and-white cat) /KAL-uh-koh/ A tortoiseshell cat with white spots. These cats, which are almost exclusively female, have a patchy coloration due to random inactivation of different X chromosomes in different somatic cell lines very early in development (the primary coat color locus in cats is on the X chromosome).

calorie (cal) /KAL-er-ee/ The amount of heat needed to raise one gram of water from 14.5˚ to 15.5˚C at a pressure of one atmosphere.

calyx /KAL-iks/ The whorl of sepals that encloses a bud and subsequently embraces the base of an open flower.

cambium /KAM-bee-uhm/ The cylinder of undifferentiated embryonic tissue (meristem) that allows the stem of a plant to grow in diameter.

Cambrian (Є) /KAM-bree-uhn/ The most ancient period of the Paleozoic Era, which began 543 million years ago. Geologist Adam Sedgwick named it for Cambria, the ancient name of Wales, where he discovered the first known Cambrian deposits.

cAMP Cyclic adenosine monophosphate (cyclic AMP or cyclic 3',5'-adenosine monophosphate), a diffusable signaling molecule important in many biological processes. cAMP is synthesized from adenosine triphosphate (ATP) by adenylyl cyclase. cAMP decomposition into AMP is catalyzed by phosphodiesterase. cAMP is a "second messenger." That is, it is an signaling molecule that carries a signal of extracellular origin to some site within the cell. Generally, such signals originate from a hormone that is itself too large to enter the cell.

Canadian Shield A broad region of Precambrian rock covering most of Canada. Originating from the ancient continent of Laurentia, it formed the center around which the remainder of the North American continent formed. SEE LOCATION OF CANADIAN SHIELD

canalization /KAN-uhl-IZE-ay-shun/ A tendency to follow a particular developmental pathway despite the effect of mutation or the environment.

cancer /KAN-sir/ A sarcoma or carcinoma; malignant tumor or neoplasm.

Canidae /KAN-uh-DEE/ The mammalian family that contains dogs and other doglike animals.

canine /KAY-nine/ (1) of, pertaining to, or like dogs; (2) a pointed tooth between the incisors and premolars; in mammalian predators the canines are usually elongated and function in seizing and piercing prey.

canopy /KAN-oh-pee/ The upper level of a forest, composed of the leafy upper branches of the trees.

CAP Catabolite activator protein.

capillaries The microscopic vessels connecting the arterial system with the venous system.

capillary array An apparatus, composed of an array of gel-filled silica capillaries, used to separate DNA fragments for sequencing. The capillaries' small diameter allows application of more intense electric fields, which results in separations that are much faster than separations using slab gels.

Papillomavirus capsid

capsid The outer protein coat of a virus particle.

carbohydrate Biochemical compounds such as sugars, starch, and, chitin. They fall into three main classes, monosaccharoses, disaccharoses, and polysaccharoses. They are called carbohydrates because they (1) always contain carbon; (2) always contain hydrogen and oxygen in a two to one ratio (the same ratio as in water). DIAGRAM

carbon (C) A nonmetallic chemical element. Atomic number 6, atomic weight 12.0111. All organic compounds contain carbon, together, most commonly, with hydrogen, oxygen, and nitrogen. PERIODIC TABLE

carbon cycle A cycle composed of two primary processes, photosynthesis and respiration. Photosynthesis produces oxygen and glucose from carbon dioxide and water. Respiration reverses this by creating carbon dioxide and water from glucose and oxygen. See: respiration.

carbon dioxide (CO₂) A colorless, acid-tasting gas exhaled by all animals; one of the major greenhouse gases. The body eliminates carbon dioxide in exhaled air, urine, and perspiration. Carbon dioxide is essential to all plants, which assimilate it into organic material by photosynthesis. Plants release oxygen as a byproduct of this process.

carboxyl group (COOH or CO₂H) A carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group. A carboxyl group is present in carboxylic acids, including amino acids. MOLECULAR STRUCTURE

carboxyl terminal (C-terminal or C-terminus) The peptide chain end carrying the free alpha carboxyl group of the last amino acid. The sequence of a peptide is normally written with the C-terminus to the right.

carcinogen An agent causing cancer.

carcinoma A malignant tumor enclosed in connective tissue; tends to infiltrate and metastasize.

cardiac Of, or relating to, the heart.

caries /KARE-eez/ Decay and disintegration of bone or tooth; associated with inflammation and the formation of abscesses in the surrounding tissues or periosteum. Tooth caries is commonly known as tooth decay. Bone caries is usually tubercular.

carnivore An organism that eats meat.

carpel Female reproductive organ of a flower; made up of a stigma, a style, and an ovary.

carpus The bones of the wrist taken as a whole. SEE PICTURE

carrier protein (also transport protein) A protein that transports a specific enzyme across a biological membrane during facilitated diffusion. It has a binding site that is specific for the particular enzyme it transports.

carrying capacity The maximum population density that can be sustained by a particular type of environment.

cartilage /KART-uh-lij/ Flexible supportive tissue, such as that in the tip of the human nose. It is rich in collagenous fibers, which are suspended in a matrix of rubbery chondrin.

catabolic pathways Metabolic processes that release energy as complex molecules are broken down into simpler ones.

catabolism Disintegrating, or tearing-down, processes; the end-products of catabolism are usually excreted.

catabolite A product of a catabolic process.

catalysis /kuh-TAL-uh-sus/ The speeding of a chemical reaction by a catalyst.

catalyst /KAT-uh-list/ A molecule that increases the speed of a chemical reaction without being consumed by the reaction.

catalytic /KAT-uh-LIT-ik/ Causing or involving catalysis.

catalyze (British catalyse) /KAT-uh-lize/ To a speed chemical reaction with a catalyst.

catarrhine primates /KAT-uh-rine/ Old World monkeys, apes, and human beings.

catheter /CATH-uh-ter/ A tube for introducing liquids into, extracting them from, the body.

catheterization (British: catheterisation) /CATH-uh-ter-eye-ZAY-shun/ State of being fitted with a catheter.

cation A positively charged ion.

caudad /CAW-dad/ Toward the tail or in a posterior direction.

caudal /CAWD-uhl/ (1) pertaining to the tail; (2) inferior in position.

cauterize (British: cauterise) /CAWT-uh-rize/ To burn tissue in order to destroy or sterilize it.

cautery /CAWT-uh-ree/ A means of cauterizing tissue.

cc Cubic centimeter.

CD (1) cluster of differentiation; (2) circular dichroism; (3) curative dose.

CD molecule Cluster of differentiation molecule.

cDNA Complementary DNA.

cDNA clone A cDNA sequence carried in a cloning vector.

cDNA library A library of cDNA sequences.

CDP Cytidine diphosphate.

CDR Complementarity determining region.

cecum /SEE-kuhm/ A blind pouch forming the first section of the large intestine. PICTURE

cell DEFINITION OF CELL

cell biology See: cytology.

cell line See: clone.

cell membrane See: plasma membrane.

cell plate A double membrane that forms at the equator of dividing plant cells during mitotic telophase. A new cell wall forms between the two membranes.

cell sap The liquid inside a vacuole.

cell wall (1) in some eukaryotic cells, a rigid capsule enclosing the plasma membrane; in plants it contains cellulose and lignin; in fungi, chitin; (2) in prokaryotes, a stiff capsule enclosing the cell membrane.

cellulose /SELL-yuh-loas/ Fibrous carbohydrate that acts as a structural framework of plants; indigestible by humans, but serves as a food source for many other organisms.

centimorgan (cM) /SENT-uh-MORE-guhn/ See: Morgan unit.

Central Nervous System 1. Brain 2. Central nervous system (brain and spinal cord) 3. Spinal cord

central nervous system (CNS) In a vertebrate, the primary portion of the nervous system. It is composed of the brain and spinal cord.

centrifugate /sen-TRIF-yuh-guht/ A product of centrifugation.

centrifugate /sen-TRIF-yuh-gate/ To subject to centrifugation.

centrifugation /sen-truh-f(y)oo-GAY-shun/ Processing with a centrifuge.

centrifuge /SEN-truh-fyooj/ A machine used to separate the constituents of liquid mixtures by spinning them at high speeds.

centromere /SEN-truh-meer/ The region of a chromosome where the sister chromatids attach to each other and to which spindle fibers attach during mitosis and meiosis. MORE INFORMATION ON CENTROMERES

CG Chorionic gonadotropin.

chaetognaths (common name: arrow worms) /KEED-uhg-naths, -nuhths/ Small worms in the phylum Chaetognatha (chaeto = bristly and gnath = jaw). They range in size from 2 mm to 12 cm in length, depending on the form in question, and occupy a broad range of marine environments. Most chaetognaths are transparent. PICTURE | PICTURE | ANATOMY

chaetotactic. /kee-doh-TACK-tick/ Pertaining to chaetotaxy.

chaetotaxy. /kee-doh-TACKS-ee/ The study of the arrangement of bristles on arthropods.

cheilectropion (also chilectropion). /kigh-lek-TROPE-ee-awn, -uhn/ Eversion of the lips.

chimera (also chimaera). /kigh-MIR-uh, kuh-/ (1) an organism conbining cells from two or more different genetic sources. A chimera can be produced, for example, by pushing together two genetically distinct early-stage embryos and then allowing them to develop; (2) a molecule composed of molecules of two distinct types (e.g., a DNA-RNA chimera).

chimeraplasty An experimental targeted repair process in which a synthetic DNA/RNA chimeric molecule (chimeraplast) is used to repair single base pair mutations, deletions, or insertions in DNA. A desirable sequence of DNA is combined with RNA to form the chimeraplast. These chimeric molecules bind selectively to the target DNA that is to be repaired. Once bound, the chimeraplast activates a natural gene-correcting mechanism and the mutated gene is repaired. Chimeraplasty makes no use viruses or other conventional vectors. See also: gene therapy, cloning vector.

chitin /KIGHT-in/. A structural polysaccharide that is the main component of the exoskeletons of all arthropods and the cell walls of fungi. It is also found in many mollusks, for example, in radulae and in the beaks of cephalopods. Chitin is a high-molecular-weight polymer made up of N-acetylglucosamine residues. STRUCTURE OF TWO LINKED RESIDUES

Chl Chlorophyll.

chlorine (Cl) /KLORE-een/ Chemical element (atomic weight 35.453, atomic number 17). A corrosive, poisonous gas. When inhaled, it destroys the mucous membranes of the respiratory passages (this effect can be countered by inhaling ammonia or alcohol fumes). Combines with sodium to form common salt (NaCl). PERIODIC TABLE

chlorophyll (Chl) /KLORE-uh-fill/ The green coloring matter found inside chloroplasts; in photosynthesis it catalyzes the combination of carbon dioxide with water to form carbohydrates.

Constituents of a chloroplast

chloroplasts /KLORE-uh-plasts/ Plant organelles where photosynthesis occurs. A schematic view of a chloroplast appears at right. A double membrane encloses an internal thylakoid network. Stacks of thylakoids are called grana (sing. granum). Chloroplasts, which are though to be the descendants of endosymbiotic cyanobacteria, have circular chromosomes like those of prokaryotes.

cholemesis /kole-EM-uh-suhs/ Presence of bile in the vomitus.

cholera /CALL-er-uh/ An acute infectious form of gastroenteritis caused by endotoxin-producing strains of the bacterium Vibrio cholerae. Contagion is through ingestion of foods and liquids contaminated with the excreta of infected individuals. SEM: V. CHOLERAE

chondrin /CAWN-drin, -druhn/ A gelatinous protein-carbohydrate complex present in cartilage.

chondriome /KOND-ree-ome/ All the mitochondria of a cell taken together.

chondrosarcoma /KON-droh-sar-KOH-muh/ A sarcoma forming in bone cartilage (except "extraskeletal chondrosarcoma", which forms, not in bone cartilage, but in the soft tissues of the upper arms or legs). Chondrosarcoma is more common in people over 40.

Chordata /KORE-dot-uh/ The phylum of animals in which the embryo passes through a stage in which a notochord and gill slits are present; includes all fishes, amphibians, reptiles, birds, and mammals.

chordate /CORE-date, -duht/ Of, relating to, or a member of Phylum Chordata.

chorea /kore-REE-uh/ A disorder characterized by involuntary, spasmodic movements of the face and extremities.

chorioadenoma /kore-ee-oh-AD-uh-NOME-uh/ Adenoma of the chorion.

choriocele /KORE-ee-oh-seel/ Bulging of the choroid coat through a ruptured sclera.

chorion /KORE-ee-awn/ The outermost of the four membranes surrounding a mammalian embryo.

chorionic gonadotropin (CG) /kore-ee-AWN-ik guh-NAD-uh-TROPE-uhn/ A hormone stimulating production of progesterone. It is itself produced by the placenta and is the hormone usually assayed for by pregnancy tests.

choroid (also chorioid) /KORE-oid, KORE-ee-oid/ One of the eye's coats. Composed of dark brown vascular tissue, it lies between the sclera and retina. PICTURE

chromatid /KROME-uh-tid/ One of the two identical strands of a single replicated chromosome, which are joined at the centromere. PICTURE

chromatin /KROME-uh-tuhn, -tin/ The substance of which eukaryotic chromosomes are composed. It is itself composed of DNA, RNA, and proteins.

chromomere /KROME-uh-meer/ One of the beads of locally coiled DNA visible on a eukaryotic chromosome during meiotic prophase I.

chromonema (pl chromonemata) /KROME-oh-NEEM-uh/ The thread of DNA within chromatin.

chromoplasts /KROME-uh-PLASTS/ Plastids found in flowers and ripe fruits; they contain carotenoids (lipid soluble pigments ranging from yellow to red in color), which lend color to the plant tissues that contain them.

chromosomal mutations /krome-uh-SOAM-uhl/ Changes in the karyotype; may involve a translocation, an inversion, aneuploidy, or polyploidy. MORE INFORMATION

chromosome /KROME-uh-soam/ A physically discrete portion of the genome carrying many genes. A chromosome is composed of chromatin. Prokaryotic chromosomes are single and circular. Eukaryotic chromosomes are multiple and linear. MORE INFORMATION

chromosome number (also chromosome count) /KROME-uh-soam/ The number of chromosomes in a eukaryotic cell. Each eukaryote has a characteristic chromosome number, which is the typical number of chromosomes found in each of its cells.

chromosome painting /KROME-uh-soam/ Attachment of a fluorescent dye to particular chromosomes, or parts of a chromosome having an affinity for the dye. See: spectral karyotype.

chromosome pair (also homolog pair) /KROME-uh-soam/ A pair of homologs.

chromosome set /KROME-uh-soam/ (1) in an organism that lacks sex chromosomes: a set of chromosomes that includes one and only one of each of the different types of chromosomes characteristic of that organism; (2) in an organism having sex chromosomes: a set of chromosomes that includes one and only one of each of the different types of autosomes characteristic of that organism, plus either one of the sex chromosomes.

chronobiology /KROH-no-bye-AWL-uh-gee/ The study of time-dependent phenomena in living organisms.

chronospecies /KROH-no-SPEE-seez/ A fossil form assigned a distinct binomial name because it occurred at a different time from other, similar forms. However, there is no generally accepted definition of the term species (more information).

chrysalis /CHRIS-uh-liss/ An enclosed, immobile stage during the development of many insects that undergo metamorphosis.

cilia (sing cilium) /SILL-ee-uh,SILL-ee-uhm/ (1) eyelashes; (2) tiny hairlike processes covering certain internal surfaces of the body such as the epithelial surfaces of the respiratory tract or the internal lining of the inner ear.

Cl Chlorine.

clade A hypothesized group consisting of a single common ancestral form and its descendant forms, usually thought of as being produced by divergence. MORE INFORMATION

cladistics /kluhd-IST-iks, klad-/ A school of taxonomic thought that holds that organisms should be classified on the basis of evolutionary relationship. Compare: phenetics. MORE INFORMATION

cladogenesis /KLAD-oh-JEN-uh-suhs/ Evolutionary change that produces a clade. Compare: anagenesis.

class In taxonomy, a division of a phylum that itself contains one or more orders. CHART OF RELATIVE TAXONOMIC RANKS

cleidoic egg /kligh-DOE-ik/ A shelled egg permeable only to gases.

cleistogamy /kligh-STAW-guh-mee/ Self-pollination that occurs before the flower opens.

cline A graded series of differences exhibited within a population (usually along a geographic line or across a region of environmental transition).

clomiphene A chemical stimulant that causes ovaries to release eggs.

clone Two or more molecules, cells, or organisms identical to some ancestral molecule, cell, or organism. MORE ABOUT ORGANISMAL CLONES

clone bank See: genomic library.

cloning (1) producing multiple, exact copies (clones) of a single segment of DNA to obtain sufficient material for further study. This process is called "cloning DNA." The resulting collections of cloned DNA molecules are referred to as "clone libraries" (see: cloning vector); (2) producing by the natural process of cell division many copies of a cell. The collection of cloned cells identical to the original cell, is called a cell line. (3) producing complete, genetically identical organisms via mitosis (read more about organismal clones). See also: cloning vector.

cloning vector A virus, plasmid, bacteriophage, chromosome, or eukaryotic cell used to carry and replicate a DNA sequence of interest so that more copies of that DNA can be produced; also can be used for producing the protein product of a particular DNA sequence.

Clostridium A genus of anerobic, spore-forming bacilli to which the microorganisms causing gangrene, botulism, and tetanus belong. PHOTOMICROGRAPH OF CLOSTRIDIUM DIFFICILE

cluster of differentiation molecules (CD molecules) Cell-surface molecules that are recognized by particular sets of monoclonal antibodies. CD molecules are used to identify cell types, and the stage of differentiation and activity of cells. As soon as two specific monoclonal antibodies (mAb) have been shown to bind to a particular CD molecule, it is assigned a number. If the molecule has not been well characterized, or has only one mAb, it is usually assigned the provisional indicator w (e.g., "CDw29"). The CD designation system was originally conceived for the classification of leukocytes, but is now used for a wide variety of cell types.

C-meiosis /my-OH-suhs/ Colchicine blocked meiosis.

C-metaphase /MET-uh-faze/ Colchicine blocked metaphase.

C-mitosis /my-TOE-suhs/ Colchicine blocked mitosis; treating mitotic cells with colchicine allows easier detection and identification of chromosomes than in normal mitosis. During the long metaphase of a C-mitosis the chromosomes are still connected at the centromere, but the chromatids of each chromosome pair repel each other. The chromatids do eventually separate, but they don't segregate. Instead, a single nuclear envelope develops and encloses them all. The individual chromatids then replicate during interphase state. The result is a cell with a doubled chromosome count. For example, diploid cells treated with colchicine yield tetraploid cells.

CM Carboxymethyl.

CMP (1) cytidine monophosphate; (2) cAMP receptor protein (catabolite activator protein).

CNS Central nervous system.

Cnidaria /nigh-DAR-ee-uh/ The phylum containing jellyfishes, sea anemones, and hydroids. The diagnostic feature of a cnidarian is the cnidocyte, a cell that fires a toxin projectile — the cnidocyst or nematocyst — this administers a sting. The body of a cnidarian is made up primarily of mesoglea contained in a bag of thin epithelium.

cnidarian /nigh-DAR-ee-uhn/ Of, relating to, or a member of Phylum Cnidaria.

Discharged cnidocyst

cnidocyte /NIGH-duh-sight/ See: Cnidaria.

CoA Coenzyme A.

CoA-SH Reduced coenzyme A.

code See: genetic code.

coding strand The strand of a duplex DNA molecule that has the same nucleotide sequence as the mRNA (except that Ts appears in the DNA where Us appear in the corresponding RNA). The coding strand is antisense strand because it does not serve as the template for mRNA synthesis.

codominant genes /ko-DAWM-uh-nuhnt/ Genes with two alleles that are fully expressed in the heterozygote. See also: autosomal dominant, recessive gene.

codon /KO-dawn/ See: genetic code.

coefficient of variation (C or C.V.) /ko-uh-FISH-uhnt/The standard deviation divided by the mean and multiplied by 100.

coenzyme /KO-ehn-zime/ An organic molecule required for an enzyme's function. Most vitamins are coenzymes.

coenzyme A (CoA) /KO-ehn-zime/ An important intermediate in the metabolism of fatty acids, amino acids, and pyruvate.

coenzyme Q₁₀ (also coenzyme Q, ubiquinone, ubidecarenone, abbreviations: CoQ₁₀-- pronounced KOH-cue-tehn -- CoQ, Q10, Q) /KO-ehn-zime/ A molecule present in most eukaryotic cells, especially the mitochondria. As a component of the electron transport chain, it takes part in aerobic respiration, generating energy in the form of ATP.

cofactor /KO-fak-ter/ Any molecule or ion required for an enzyme's function.

cohort /KO-hort/ In a population, all individuals of given age.

coisogenic strains /KO-ice-uh-GEN-ik/ Nearly identical strains differing at only a single locus. Compare: congenic strains.

Unfolded wing of beetle (click to enlarge)

Half-folded wing, elytron removed (click to enlarge)

Fully folded wing, elytron removed (click to enlarge)

Coleoptera /KOH-lee-AHP-ter-uh/ The largest insect order, containing the beetles. The name is derived from beetles' ability to sheath their wings (Coleo- = sheath and -ptera = wing). See figures at right. The sheath with which a beetle covers its folded wings is called an elytron.

coleoptile /koh-lee-OP-tuhl/ The first leaf of a monocotyledon.

collagen /KO-luh-jen/ A long, fibrous structural protein that supports tissues and gives structure to individual cells. Collagen is also an important component of the matrix interconnecting cells. Collagen fibers are tough and typically bundled. They provide tensile strength to the tissues that contain them. Collagen is also found inside certain cells. It is a primary constituent of cartilage, ligaments, fascia, bone, and skin.

colloid /KOHL-oid/ A substance, such as starch, albumin, or gelatin, that shows little or no tendency to diffuse across membranes even when thoroughly mixed with a liquid. A colloid mixed with a liquid is not actually dissolved and does not cause some of the effects usually associated with a solute (e.g., increases in the freezing point, boiling point, and vapor pressure of the liquid).

colon /KO-luhn/ See: large intestine.

commensalism /kuh-MEN-suh-LIZ-uhm/ A form of symbiosis in which one of the two participants benefits, but the other is not harmed.

comparative genomics /juh-NOME-iks/ A method of bioinformatic analysis that characterizes genetic motifs by comparing the genomes of different model organisms.

complementary DNA (cDNA) A DNA sequence generated from an RNA (usually mRNA) template. If the introns have been processed out of the RNA, the resulting cDNA will differ from the gene that originally produced the RNA. See also: messenger RNA

complementary sequence A single-stranded nucleotide sequence that can form a double-stranded structure with another single-stranded sequence. For example, the complementary sequence to CATG is GTAC.

complex trait A non-Mendelian trait that does not follow the ordinary pattern of inheritance. Usually involves interaction of two or more genes or interactions between a gene and the environment. See also: additive genetic effects.

computational biology See: bioinformatics.

concerted evolution /kuhn-SERT-uhd/ Evolution of a gene family in which members of the family occurring at different loci in the same type of organism remain more similar to each other than are versions of occurring at the same locus in distinct types of organisms.

congenic strains /kuhn-JEN-ik/ Nearly identical strains differing only with respect to a small chromosomal segment. Compare: coisogenic strains.

congenital trait /kuhhn-JEN-uh-tuhl/ A trait present at birth.

conglomerate /kuhn-GLOM-er-ruht/ Coarse-grained (clasts > 2mm in diameter) sedimentary rock.

coniology See: koniology.

conjunctiva /kuhn-juhnk-TIGH-vuh/ Clear mucous membrane that lines the sclera and the interior of the eyelids.

connective tissue /kuh-NECK-tiv, -tuhv/ One the four categories to which tissue has traditionally been assigned, the other three being muscle, epithelial, and nervous tissue. Under this system, any tissue that does not fall into one of these last three categories (muscle, epithelium, or nervous tissue) is classed as "connective."

conotoxins /ko-no-TAWKS-uhns/ Toxins produced by snails of the genus Conus.

conservation biology The branch of biology concerned with habitat preservation, the prevention of extinction, and conservation of biodiversity.

conserved sequence A nucleotide or amino acid sequence that is similar in two or more distinct types of organisms.

contig /KAWN-tig/ A nucleotide sequence constructed by assembling overlapping cloned nucleotide sequences. A contig represents a region of some particular chromosome.

Fly in copal

contig map /KAWN-tig/ A genetic map depicting the relative order of the overlapping clones lying within a contig.

convergence /kuhn-VER-juhnce, -jence/ Any similarity between organisms not considered to reflect relationship. See: homologous traits, homology MORE INFORMATION

contraceptive /KAWN-truh-SEP-tiv/ Any device or drug preventing pregnancy.

copal /KO-puhl, ko-PALL/ A resin produced by tropical trees; many fossil insects have been found in copal. The preservation can be exquisite, with many of these ancient insects retaining every detail and color -- even of the wings and eyes.

copper (Cu) /KAWP-er/ Chemical element; atomic weight: 63.546, atomic number: 29. Required in small amounts bz all plants and animals. Its salts, however, are poisonous. Normally, the human body contains about 1.4 to 2.1 mg of copper for each kg of body weight. Copper is present in many enzymes, including cytochrome c oxidase and superoxide dismutase. For oxygen transport, most mollusks and certain arthropods use the copper pigment hemocyanin instead of hemoglobin. As a result, their blood is blue, not red, when oxygenated. Due to its facilitation of iron uptake, copper deficiency can cause anemia and impaired respiration. PERIODIC TABLE

coprolites /KAWP-ruh-lites/ Pieces of fossilized excrement. Coprolites can be analyzed to determine the diets of extinct organisms.

coprophilic /KAWP-ruh-FILL-ik/ Attracted to excrement.

coprozoic /KAWP-ruh-ZOH-ik/ Living in excrement.

CoQ or CoQ₁₀ Coenzyme Q₁₀.

cord An anatomical structure resembling an ordinary cord, as a spinal cord.

correlation /kor-uh-LAY-shun/ The degree to which two statistical variables vary together; usually measured in terms of the correlation coefficient.

correlation coefficient (r) /kor-uh-LAY-shun/ A common measure of correlation, r = cov(x,y)/s_xs_y, where cov(x,y) is the covariance between samples x and y, s_x is the standard deviation of sample x, and s_y is the standard deviation of sample y. Note that 1 ≥ r ≥ -1, and that r = 1 indicates a perfect positive correlation, r = -1 indicates a perfect negative correlation, and r = 0 indicates a lack of correlation.

cosmid /KAWZ-mid/ DEFINITION OF COSMID

cotyledon /ko-TILE-uh-dawn/ An embryonic seed leaf. The cotyledons function in absorbing nutrients from the seed before the embryo is sufficiently developed to be capable of photosynthesis. Angiosperms are classified as one of two major types, either monocotyledons or dicotyledons, on the basis of the number of cotyledons present in the embryo.

Two carbons sharing four electron pairs

covalent bond /ko-VALE-unht/ A strong chemical bond where two atoms share a single pair of electrons.

covariance (cov) /ko-VARE-ee-uhns, KO-vare-ee-uhns/ The covariance is used to calculate the correlation coefficient. For samples of size N, the covariance between samples x and y is defined by the formula cov(x,y) = [(x₁ - xbar)(y₁ - ybar) + (x₂ - xbar)(y₂ - ybar) +, ..., + (x_N - xbar)(y_N - ybar)]/N, where xbar is the mean of sample x, and ybar is the mean of sample y.

Cowper's glands A pair of pea-sized glands on either side of the prostate that secrete fluids into the urethra.

coxa (plcoxae) /COCK-suh/ (1) the hip; (2) the hip joint.

cpm Counts per minute (of radioactivity).

cranial /KRAYN-ee-uhl/ Of, or relating to, the cranium.

cranial capacity /KRAYN-ee-uhl/ The volume of an individual's braincase (usually measured in cubic centimeters).

cranium /KRAYN-ee-uhm/ The portion of the skull enclosing the brain.

craton /KRAY-tawn, KRAT-tawn/ A (continental) portion of the Earth's curst that is stable and that has not undergone deformation for a long period of time; adj.: cratonic /kruh-TAWN-ik, kray-, krat-/.

Cretaceous-Tertiary (KT) mass extinction /kruh-TAY-shuhs TARE-she-air-ee -shair-ee/ The mass extinction that occurred at the end of the Cretaceous Period (and of the Mesozoic Era). It is generally believed that the dinosaurs became extent at this time (this issue is discussed at length elsewhere on this website).

North America in the Cretaceous

Cretaceous Western Interior Seaway /kruh-TAY-shuhs/ A sea that divided the eastern and western portions of North America from around 130 to 70 million years ago. It stretched from the Arctic to the Gulf of Mexico, and at its widest, in the Middle Cretaceous, it extended from present-day Utah to the Appalachian Mountains. For this reason marine fossils are common in the Great Plains region of North America.

crocodilians /krock-uh-DILL-ee-uhns/ Alligators, crocodiles, and gharials.

crossing over The exchange of genetic material between homologs during prophase I of meiosis. See also: recombination.

crust The outermost layer of the Earth. The crust is thinnest — about 6 miles (~10 km) thick beneath the oceans — and thickest — about 40 miles (~65 km) beneath the the continents. The crust makes up less than 1 % of the Earth's volume.

crustacean An animal belonging to the major arthropod group Crustacea, which is composed mostly of such familiar marine animals as crabs, shrimp, and lobsters.

cryobiology /cry-oh-bye-AWL-uh-gee/ The study of the effects of low temperatures on living organisms.

cryophile /CRY-uh-file/ A cold-loving organism.

C-terminal (or C-terminus) Carboxyl terminal

CTP Cytidine triphosphate.

cuneiform (also cuneate) /kyoo-NAY-uh-form, KYOO-ee-ate -uht/ Wedge-shaped.

cusp /KUHSP/ A point on the occlusal surface of a tooth; (2) one of the flaps of a cardiac valve; (3) in botany, any rigid pointed structure.

cutaneous /kyoo-TANE-ee-uhs/ Of or pertaining to skin.

cuticle /KYOOT-uh-kuhl/ (1) outermost layer or investment of an organism, particularly the exoskeleton an arthropod; usually made up of fibrous materials such as collagen or chitin, and in some cases strengthened by the addition of minerals (e.g., calcium carbonate) (2) a waxy external layer, that prevents drying; found on the outer surface of many plants.

cutis /KYOO-tuhs/ The skin.

cyanobacteria /sigh-AN-oh-bac-TEER-ee-uh/ Photosynthetic prokaryotes, known from the earliest stages of the fossil record.

cyanosis /sigh-uh-NO-suhs) Bluish skin coloration due to high levels of reduced hemoglobin in the blood.

cys Cysteine.

cyst /SIST/ (1) a sac, bounded by a wall; (2) a sac surrounding a larva in a resting state; (3) a resting spore.

cysteine (Cys or C) /SIS-teen/ A nonessential amino acid. CODONS | MOLECULAR STRUCTURE

cystitis /sis-TIGHT-uhs/ Inflammation of the bladder.

cytidine /SIGHT-uh-deen/ Cytosine attached to a ribose ring.

cytidine triphosphate /SIGHT-uh-deen/ Cytidine with an added triphosphate; in metabolic processes cytidine triphosphate is used as a source of energy in the same way as ATP, but its role is more specific than that of ATP, because it does not participate in as wide a variety of processes.

cytochromes /SIGHT-uh-kromes/ Ferrous proteins that play a role in electron transport in mitochondria and chloroplasts.

cytogenesis /SIGHT-uh-JEN-uh-suhs/ The origin and development of a cell.

cytogenetics /SIGHT-uh-juh-NET-iks/ The study of the physical appearance of chromosomes. See also: karyotype.

cytokinesis /SIGH-toe-kuh-NEE-suhs/ The division of the cytoplasm into two daughter cells that occurs after nuclear division in mitosis or meiosis.

cytology (also cell biology) /sigh-TALL-uh-gee/ The study of living cells, in particular, their physiological properties, life histories, structures, organelles, and method of division.

cytolysis /sigh-TAWL-luh-suhs/ Cell lysis.

cytolytic /sigh-toe-LIT-ick/ Causing cytolysis.

cytometer /sigh-TOM-uh-tur/ An instrument for counting the number of cells in a sample.

cytoplasm /SIGH-toe-PLAZ-uhm/ All of the contents of a cell other than the nucleus.

cytoplasmic inheritance /sigh-toe-PLAZ-mick/ See: cytoplasmic trait.

cytoplasmic trait /sigh-toe-PLAZ-mick/ A trait governed by genes found outside the nucleus in mitochondria or chloroplasts. Such traits are inherited only from the mother. Such inheritance is known as cytoplasmic, or uniparental, inheritance.

cytosine (C) A pyrimidine base found in DNA and RNA. In duplex DNA it pairs with guanine. See also: base pair, nucleotide.

cytoskeleton /SIGH-toe-SKEHL-uh-tuhn/ A fibrous network of microtubules and microfibers in eukaryotic cells that gives shape to the cell, anchors organelles, serves a variety of transport functions within the cell, and, in some cases, allows the cell to move or change shape.

cytosol /SIGH-toe-sawl/ The fluid portion of cytoplasm.

cyturia /sigh-TER-ee-yuh/ Presence of cells (of any type) in the urine.