Chromosome: The self-replicating genetic structures containing the cellular DNA assembly that bears in its nucleotide sequence the linear array of genes. Human chromosome is present in 23 pairs; in a pair one originates from the father, the other from the mother. Such paired chromosomes form a homologous pair and the cells which contain them are said to be diploid. When the chromosomes in a cell are unpaired, as in matured sex cells, the cells are called haploid.



Chromosomal translocation: Rearrangement of a chromosome in which a segment is moved from one location to another, either within the same chromosome or to another chromosome. This is sometimes reciprocal, when one fragment is exchanged for another.
Circadian rhythm: The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs, and stimuli, hormone secretion, sleeping, feeding, etc. This rhythm seems to be set by a “biological clock” which in turn set by recurring daylight and darkness.
Cirrhosis: Liver disease characterized by destruction of normal architecture and formation of fibrous nodule. In advanced stages fluid may form in the abdomen and jaundice (increase in bile pigment) may develop.
Cis conformation: Denotes a chemical structure in which designated atoms reside on the same side of a chemical bond between two other atoms.
Cisplatin: A platinum coordinated compound, used as an antineoplastic agent, primarily for treatment for testicular carcinoma, also for carcinomas of the bladder, ovary, head and neck, and prostate. It forms DNA adducts.

Cisplatin is shown in green; it forms an adduct between two guanines in the same chain of DNA.

Clonal colony: Colony of cells developed from proliferation of a single cell.
Cloning DNA: The production of many identical copies of a specific DNA fragments usually carried out in an eukaryotic or bacterial host. The target DNA fragment is introduced in the host cell by recombinant technology.
Clonogenic: Arising from or consisting of a clone.
Cockayne’s syndrome: A hereditary syndrome consisting of dwarfism, with retinal atrophy and deafness associated with mental retardation and photosensitivity.
Codon: A set of three adjacent bases on a single strand of DNA or RNA. Of the 64 different codons, 61 direct the incorporation of specific amino acids into a protein chain and three, signal chain termination.
Coenzyme Q: A quinone derivative with a tail made up of ten isoprene units (also known Q10). It participates in the respiratory chain during energy production in the mitochondria.
Cohort: In epidemiology, a group of individuals who share a common characteristic, for example, all of the individuals born in one year, a birth cohort.
Colectomy: Excision of a part of the colon.
Collagen: The protein substance of the white fibers (collagenous fibers) of skin, tendon, bone, cartilage, and all other connective tissue.
Collagenase: An enzyme that breaks down peptide bonds (bonds connecting two aminoacids) in collagen, a special type of protein present in connective tissues such as skin, bone, and cartilage.
Colloidal solution: A solution where the particles of the dispersed phase are larger than the ordinary crystalloid molecules, but are not large enough to settle and they resist diffusion. They range in size from 1 to 100 nm or up to 500 or 1000 nm.
Colon: The major portion of the large intestine, which receives the undigested part of the food, containing water. Water is absorbed here and the rest of the material is transferred to the rectum for elimination.
Colonoscopy: The technique to observe the entire length of the colon through a flexible instrument. A fiber-optic instrument called colonoscope is inserted through the rectum and during observation tissue specimen can be collected.
Colostomy: The surgical procedure when an opening is made from the colon to the surface of the body for the purpose of excretion and a plastic pouch is attached for drainage.
Colposcopy: Examination of cervix and vagina with the help of colposcope, an instrument with magnifying glass.
Complement: Distinct serum proteins participating in immune cytolysis.
Conformation: Spatial orientation of molecules.
Conformational change: Change in the spatial geometry of molecules.
Constant-region: The stem and forking part of the Y-shaped antibody protein, consisting of amino acid chains, that is exactly the same in all antibody molecules within the same individual. (The ends of the Y-shaped molecule will vary widely between different antibodies).
Cori cycle: The conversion of glucose to lactate in muscle followed by partial resynthesis of glucose from lactate in the liver and its return to the muscles.
Coronary Heart Disease: Disease of the arteries that supply blood to the heart muscles.
Corpus luteum: A yellow glandular mass in the ovary formed by an ovarian follicle that has been matured and discharged its ovum.
C-reactive protein: A protein produced by the liver during periods of inflammation and detectable in serum in various disease conditions particularly during the acute phase of immune
Crohn’s disease: A chronic granulomatous inflammatory disease involving any part of the gastrointestinal tract with scarring and thickening of the bowel wall; it frequently leads to intestinal obstruction.
CT Scan: Also known as CAT scan, computer aided tomography. This technique uses computers and X-ray to obtain detailed image of a part of the body.
C-terminal: In proteins the amino acid building blocks are connected forming amide bond between the carboxyl (-COOH) group of the first amino acid and the amino (-NH2) group of the second. The progressing chain of this polypeptide is the C-terminal end. See diagram below:



Cyanobacteria: A group of photosynthetic bacteria also known as blue-green algae, produce oxygen in presence of light and fix both carbon dioxide and nitrogen.
Cyclin-dependent kinases: Protein kinases that control cell cycle progression in all eukaryotes and require physical association with cyclins to achieve full enzymatic activity. Cyclins are regulatory proteins that function in the cell cycle to activate maturation-promoting factor. Cyclin-dependent kinases are regulated by phosphorylation and dephosphorylation events.
Cytochrome P450: Cytochrome denotes of any iron containing protein that participates in the oxidation-reduction system involved in electron transfer. P450 is a trivial name for enzymes present in microsomes involved in the detoxification of many drugs.
Cytogenetics: The branch of genetics devoted to study of the cellular constituents concerned in heredity, that is, the chromosomes.
Cytokines: A generic term for nonantibody proteins released by one cell population, for example activated T lymphocytes, on contact with a specific antigen, which act as intercellular mediators.
Cytology: The study of cells, their origin, structure, function and pathology.
Cytopenia: A reduction in the number of cells circulating in the blood.
Cytosol: The liquid medium of the cytoplasm, that is, cytoplasm minus organelles and nonmembranous insoluble compounds.
Cytotoxic: Poisonous to cells.