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Medical Dictionary


gelsolin (jel-sol′in)
An actin-binding protein; a Ca2+-triggered actin-filament-severing protein; hence, it has roles in locomotion, secretion, and endocytosis.

Jules A., French surgeon, 1806–1861. See G. suture.

Prefix denoting twin substitutions on a single atom; e.g., the g.-dimethyl substitution on carbon-4 of lanosterol. [L. geminus, twin]

Gemella (je-mel′a)
A genus of motile, aerobic, facultatively anaerobic, coccoid bacteria (family Streptococcaceae) that occur singly or in pairs, with flattened adjacent sides. They are Gram-indeterminate but have a cell wall like that of Gram-positive bacteria, and are parasitic on mammals. The type species is G. haemolysans, which is found in bronchial secretions and in mucus from the respiratory tract. [L. dim. of geminus, twin] G. morbillorum a microaerophilic bacterium, formerly called Streptococcus morbillorum, that fails to produce β-hemolysis of blood agar and lacks distinguishing serogroup antigens; causes serious infections in some patients similar to those seen with viridans streptococci.

gemellology (jem-el-ol′o-je)
The study of twins and the phenomenology of twinning. [L. gemellus, twin-born, + G. logos, study]

gemellus (je-mel′us)
SYN: inferior g. (muscle), superior g. (muscle). [L. dim. of geminus, twin]

gemfibrozil (jem-fi′bro-zil)
An antihyperlipidemic agent.

geminate (jem′i-nat)
Occurring in pairs. SYN: geminous. [L. gemino, pp. -atus, to double, fr. geminus, twin]

gemination (jem-i-na′shun)
Embryologic partial division of a primordium. For example, g. of a single tooth germ results in two partially or completely separated crowns on a single root. [L. geminatio, a doubling]

geminous (jem′i-nus)
SYN: geminate.

gemistocyte (je-mis′to-sit)
SYN: gemistocytic astrocyte. [G. gemistos, loaded, fr. gemizo, to fill, + -cyte]

gemistocytoma (je-mis′to-si-to′ma)
SYN: gemistocytic astrocytoma.

gemma (jem′a)
Any budlike or bulblike body, especially a taste bud or end bulb. [L. bud]

gemmation (jem-a′shun)
A form of fission in which the parent cell does not divide, but puts out a small budlike process (daughter cell) with its proportionate amount of chromatin; the daughter cell then separates to begin independent existence. SYN: bud fission, budding. [L. gemma, a bud]

gemmule (jem′ul)
1. A small bud that projects from the parent cell, and finally becomes detached, forming a cell of a new generation. 2. SYN: dendritic spines, under spine. [L. gemmula, dim. of gemma, bud] Hoboken gemmules SYN: Hoboken nodules, under nodule.

Being born, producing, coming to be. [G. genos, birth]

Suffix denoting “precursor of.” SEE ALSO: pro- (2) .

gena (je′na)
SYN: cheek. [L.]

genal (je′nal)
Relating to the gena, or cheek.

gender (jen′der)
Category to which an individual is assigned by self or others, on the basis of sex. Cf.:sex, g. role.

gene (jen)
A functional unit of heredity that occupies a specific place (locus) on a chromosome, is capable of reproducing itself exactly at each cell division and directs the formation of an enzyme or other protein. The g. as a functional unit consists of a discrete segment of a giant DNA molecule containing the purine (adenine and guanine) and pyrimidine (cytosine and thymine) bases in the correct sequence to code the sequence of amino acids of a specific peptide. Protein synthesis is mediated by molecules of messenger-RNA formed on the chromosome with the g. acting as a template. The RNA then passes into the cytoplasm and becomes oriented on the ribosomes where it in turn acts as a template to organize a chain of amino acids to form a peptide. In organisms reproducing sexually, normally occur in pairs in all cells except gametes, as a consequence of the fact that all chromosomes are paired except the sex chromosomes (X and Y) of the male. SYN: factor (3) . [G. genos, birth] allelic g. See allele, dominance of traits. autosomal g. a g. located on any chromosome other than the sex chromosomes (X or Y). BRCA1 g. a tumor suppressor g. on chromosome 17 at locus 17q21, isolated in 1994; encodes p53 protein, which prevents cells with damaged DNA from dividing; carriers of germline mutations in BRCA1 are predisposed to develop both breast and ovarian cancer. SEE ALSO: BRCA2 g., carcinoma of the breast. BRCA2 g. a tumor suppressor g. identified in 1995 on chromosome 13 at locus 13q12–q13; a large g. consisting of 27 exons distributed over 70kb, encoding a protein of 3418 amino acids; carriers of germline mutations in BRCA2 have an increased risk, similar to that of those with BRCA1 mutations, of developing breast cancer and a moderately increased risk of ovarian cancer; BRCA2 families also exhibit an increased incidence of male breast, pancreatic, prostate, laryngeal, and ocular cancers. SEE ALSO: BRCA1 g., carcinoma of the breast.Familial clustering of breast cancer has long been recognized. Familial breast cancers are characterized by onset before age 45 and by clustering in 3 or more close relatives and in members of more than 1 generation. About 5% of all breast cancers are due to the inheritance of dominant susceptibility genes, particularly BRCA1 and BRCA2. Whereas spontaneous mutations of the BRCA genes are uncommon, hundreds of inherited mutations have been discovered on each g.. The clinical significance of many of these is unknown. Since these are autosomal chromosomes, men as well as women can inherit and pass on the BRCA mutations. The histology of breast cancer in women with BRCA1 and BRCA2 mutations differs from that of sporadic cases. The proportion of medullary carcinomas is higher among BRCA1-associated breast cancers than among all breast cancers. BRCA1 and BRCA2 are tumor suppressor genes, inhibiting tumor development when functioning normally. Both are large genes encoding large negatively charged proteins. Inactivating mutations identified to date are distributed throughout both genes, with a predominance of 2 distinct mutations for BRCA1 and 1 for BRCA2. Despite the high penetrance of the mutant g., not all carriers develop cancer. Hormonal, environmental, reproductive, and other genetic factors may influence penetrance. Estradiol increases cell proliferation and production of the BRCA1 g. product in vitro, while the estrogen antagonist tamoxifen inhibits both cell proliferation and BRCA1 g. expression. Observed mutations are distributed throughout the g.; most are insertions, deletions, or nonsense mutations. Two common changes (185delAG and 5382insC, in exons 2 and 20, respectively) account for approximately 19% of BRCA1 mutations. The former of these is present in about 1% of Ashkenazic Jews and is responsible for about 32% of familial breast cancer in Jews. It is also found in 13% of ovarian cancer patients with no family history of breast or ovarian cancer, and in 30% of those with family histories suggesting inherited disease. BRCA1 mutations cause a 3-fold increase in the risk of prostate cancer in males and a 4-fold increase in the risk of colon cancer in persons of both sexes. The BRCA2 6174delT mutation is estimated to be present in 1.3% of Ashkenazic Jews. Earlier estimates of the risk that a women with a BRCA1 or BRCA2 g. mutation would develop breast cancer at some time in her life ranged from 10–90%. These figures were based on intensive study of families known to be at risk. Current estimates are that the risk of breast cancer may be no higher than 30%. In addition, 15–20% percent of women with the BRCA1 mutation will develop ovarian cancer. Although testing for BRCA genetic mutations is commercially available, most authorities do not recommend routine screening except in women with a strong family history of cancer. Women found to have BRCA genetic mutations have been advised to begin breast self-examination at age 18 and regular annual physician examinations and mammograms at age 25. The benefit of radiologic screening must be weighed against the possible effect of radiation on the BRCA1 or BRCA2 allele. In addition, mammograms are often difficult to interpret in young women because of the density of breast tissue. BRCA2 carriers are also advised to begin ovarian cancer surveillance, consisting of annual or semiannual screening using transvaginal ultrasound (TVS) with color flow Doppler and morphology index, and determination of serum CA-125 levels, at age 25–35. Support for prophylactic mastectomy and oophorectomy is waning as it becomes evident that these drastic procedures cannot altogether abolish cancer risk. Tamoxifen has been shown to reduce the risk of breast cancer in genetically predisposed women by as much as 45%. C g. the g. coding for the constant regions of immunoglobulin chains. codominant g. a set of two or more alleles, each expressed phenotypically in the presence of the other. control g. operator g., regulator g.. dominant g. dominance of traits. extrachromosomal g. a g. located outside of the nucleus ( e.g., mitochondrial genes). H g. SYN: histocompatibility g.. histocompatibility g. in laboratory animals, a g. which can elicit an immune response and thereby cause rejection of a homograft when tissue is transplanted from one individual to another; in humans, histocompatibility genes control HLA antigens. SYN: H g.. holandric g. SYN: Y-linked g.. homeotic genes a group of genes that regulate the development of the body parts by defining the boundaries of the several regions. housekeeping genes genes that are generally always expressed and thought to be involved in routine cellular metabolism. immune response genes genes in the HLA-D region of the histocompatibility complex of human chromosome 6 which control the immune response to specific antigens. jumping g. a g. associated with transposable elements. See transposon. lethal g. a g. that produces a genotype that leads to death of the organism before reproduction is possible or that precludes reproduction; for a recessive g. the homozygous or hemizygous state is lethal. microophthalmia transcription factor g. g. that when mutated causes Waardenburg syndrome type 2 and Tietz syndrome in at least some subsets of families with these autosomal dominant inherited syndromes. mimic genes nonallelic (independent) genes with closely similar effects, e.g., elliptocytosis. mitochondrial g. a functioning g. located not in the nucleus of a cell but in the mitochondrial chromosome. modifier g. a nonallelic g. that controls or changes the manifestation of a g. by interfering with its transcription. mutant g. a g. that has been changed from an ancestral type, not necessarily in the current generation. SEE ALSO: mutant, mutation. operator g. a g. with the function of activating the production of messenger RNA by one or more adjacent structural loci; part of the feedback system for determining the rate of production of an enzyme. pleiotropic g. a g. that has multiple, apparently unrelated, phenotypic manifestations. SYN: polyphenic g.. polyphenic g. SYN: pleiotropic g.. regulator g. a g. that produces a repressor substance that inhibits an operator g. when combined with it. It thus prevents production of a specific enzyme. When the enzyme is again in demand, a specific regulatory metabolite inhibits the repressor substance. repressor g. a g. that prevents a nonallele from being transcribed. SOS genes a group of genes involved in DNA repair, often induced by damage severe enough to cause stoppage of DNA synthesis. g. splicing SYN: splicing (1) . split genes genes where the genomic sequences are interrupted by intervening sequences (introns) that are spliced out of the mRNA prior to translation. structural g. a g. that codes for a specific protein or peptide. transfer genes genes carried by a conjugative plasmid, essential for fertility and establishment of the bacterial donor state. transforming g. SYN: oncogene. tumor suppressor g. a g. that encodes a protein involved in controlling cellular growth; inactivation of this type of g. leads to deregulated cellular proliferation, as in cancer. SEE ALSO: oncogene. SYN: antioncogene.In a person born with 2 normal copies of a tumor suppressor g., both copies must be inactivated by spontaneous point mutation, deletion, or failure of expression before tumor formation occurs. An inherited mutation in a tumor suppressor g. is the basis of most familial predispositions to cancer. In a person so predisposed, malignant cellular proliferation does not occur until the remaining intact copy of the g. is inactivated by deletion of part or all of its chromosome. Of many tumor suppressor genes thus far identified, the p53 g. on chromosome 17, which encodes a phosphoprotein that suppresses cell proliferation, appears to be the most important. Mutations of p53 have been found in the DNA of more than half of all human cancers studied. Li-Fraumeni syndrome, characterized by early-onset carcinomas and sarcomas, is an inherited (autosomal dominant) mutation in the p53 tumor suppressor g.. BRCA1 and BRCA2, involved in familial early-onset breast cancer and ovarian cancer, are tumor suppressor genes. V g. the g. coding for the major part of the variable region of an immunoglobulin chain. X-linked g. a g. located on an X chromosome. Y-linked g. a g. located on a Y chromosome. SYN: holandric g.. Z g. the structural g. for β-galactosidase.

genealogy (je-ne-awl′o-je)
1. Heredity. 2. The explicit assembly of the descent of a person or family; it may be of any length. [G. genea, descent, + logos, study]

gene library
A haphazard assembly of cloned DNA fragments inside of a vector which may contain genetic information about a species.

genera (jen′er-a)
Plural of genus.

generalist (jen′er-al-ist)
A general physician or family physician; a physician trained to take care of the majority of diseases not requiring surgery, sometimes including obstetrics.

generalization (jen′er-al-i-za′shun)
1. Rendering or becoming general, diffuse, or widespread, as when a primarily local disease becomes systemic. 2. The reasoning by which a basic conclusion is reached, which applies to different items, each having some common factor. stimulus g. in Pavlovian conditioning, the eliciting of a conditioned response by stimuli never before experienced but which are similar to a particular conditioned stimulus. See conditioning, classical conditioning.

generalized (jen′er-a-lizd)
Involving the whole of an organ, as opposed to a focal or regional process.

generate (jen′er-at)
1. To produce. 2. To procreate. [L. genero, pp. -atus, to beget]

generation (jen-er-a′shun)
1. SYN: reproduction (1) . 2. A discrete stage in succession of descent; e.g., father, son, and grandson are three generations. [L. generatio, fr. genero, pp. -atus, to beget] asexual g. reproduction by fission, gemmation, or in any other way without union of the male and female cell, or conjugation. SEE ALSO: parthenogenesis. SYN: heterogenesis (2) , nonsexual g.. filial g. (F) the offspring of a genetically specified mating: first filial g. (symbol F1), the offspring of parents of contrasting genotypes; second filial g. (F2), the offspring of two F1 individuals; third filial g. (F3), fourth filial g. (F4), etc., the offspring in succeeding generations of continued inbreeding of F1 descendents. nonsexual g. SYN: asexual g.. parental g. (P1) the parents of a mating, commonly experimental, involving contrasting genotypes; the original mating of a genetic experiment; parents of the F1 g.. sexual g. reproduction by conjugation, or the union of male and female cells, as opposed to asexual g.. skipped g. a phenomenon of pedigrees in which a gene is transmitted from one affected person to another through a phenotypically unaffected person, as by recessivity (especially for X-linked traits), epistasis, variable expressivity, or absence of an environmental challenge such as a toxin. Except at a crass phenotypic level ( e.g., clinical or commercial) this term becomes progressively less useful as the mechanisms are elucidated. spontaneous g. the false concept according to which living matter can arise by the vitalization of nonliving matter. SEE ALSO: biogenesis. SYN: heterogenesis (3) . virgin g. SYN: parthenogenesis.

Pertaining to generations, i.e., the discrete staging in genealogic descent.

generative (jen′er-a-tiv)
Pertaining to the process of generating.

generator (jen′er-a-ter)
An apparatus for conversion of chemical, mechanical, atomic, or other forms of energy into electricity. [g., a begetter, producer] aerosol g. a device for producing airborne suspensions of small particles for inhalation therapy or experimental work; e.g., a La Mer g., spinning disk, or vibrating reed, each of which produces a monodisperse aerosol. asynchronous pulse g. a g. in which the rate of discharge is independent of the natural activity of the heart. SYN: fixed rate pulse g.. atrial synchronous pulse g. a ventricular stimulating pulse whose rate of discharge is directly determined by the atrial rate. SYN: atrial triggered pulse g.. atrial triggered pulse g. SYN: atrial synchronous pulse g.. demand pulse g. SYN: ventricular inhibited pulse g.. fixed rate pulse g. SYN: asynchronous pulse g.. pulse g. a device that produces an electrical discharge with a regular or rhythmic waveform in which the electromotive force varies in a specific pattern in relation to time; e.g., in an electronic pacemaker, it produces an electric discharge at regular intervals, and these intervals may be modified by a sensory circuit that can reset the time-base for subsequent discharge on the basis of other electrical activity, such as that produced by spontaneous cardiac beating. radionuclide g. a column containing a large amount of a particular radionuclide (mother radionuclide) that decays down to a second radionuclide of shorter physical half-life; the daughter radionuclide is separated from the parent by the process of elution and affords a continuing supply of relatively short-lived radionuclides for laboratory use; the elution is loosely termed “milking” with the g. referred to as a “radioactive cow.” standby pulse g. SYN: ventricular inhibited pulse g.. ventricular inhibited pulse g. a g. which suppresses its output in response to natural ventricular activity but which, in the absence of such activity, functions as an asynchronous pulse g.. SYN: demand pulse g., standby pulse g.. ventricular synchronous pulse g. a pulse which delivers its output synchronously with naturally occurring ventricular activity but which, in the absence of such activity, functions as an asynchronous pulse g.. SYN: ventricular triggered pulse g.. ventricular triggered pulse g. SYN: ventricular synchronous pulse g.. x-ray g. the electronic device that controls production of x-rays in radiography; a key function is rectification of line voltage to produce a smooth direct current voltage to the x-ray tube.

generic (je-nar′ik)
1. Relating to or denoting a genus. 2. General. 3. Characteristic or distinctive. [L. genus (gener-), birth]

generic name
1. In chemistry, a noun that indicates the class or type of a single compound; e.g., salt, saccharide (sugar), hexose, alcohol, aldehyde, lactone, acid, amine, alkane, steroid, vitamin. “Class” is more appropriate and more often used than is “generic.” 2. In the pharmaceutical and commercial fields, a misnomer for nonproprietary name. 3. In the biologic sciences, the first part of the scientific name (Latin binary combination or binomial) of an organism; written with an initial capital letter and in italics. In bacteriology, the species name consists of two parts (comprising one name): the g. and the specific epithet; in other biologic disciplines, the species name is regarded as being composed of two names: the g. and the specific name.

genesial (je-ne′se-al)
Relating to generation.

genesiology (je-ne-se-ol′o-je)
The branch of science concerned with generation or reproduction. [G. genesis, generation, + logos, study]

genesis (jen′e-sis)
An origin or beginning process; also used as combining form in suffix position. [G.]

genetic (je-net′ik)
Pertaining to genetics; genetical.

geneticist (je-net′i-sist)
A specialist in genetics.

genetics (je-net′iks)
1. The branch of science concerned with the means and consequences of transmission and generation of the components of biologic inheritance. 2. The genetic features and constitution of any single organism or set of organisms. [G. genesis, origin or production] behavioral g. the study of heritable factors in behavioral patterns, as by pedigree analysis, biochemical abnormality, or karyotypic analysis. biochemical g. the study of g. in terms of the chemical (biochemical) events involved, as in the manner in which DNA molecules replicate and control the synthesis of specific enzymes by the genetic code. classical g. that body of method and analysis that perceives g. as the study of the transmission of genotype from parent to offspring; the study of multiple individuals is essential to it. clinical g. g. applied to the diagnosis, prognosis, management, and prevention of genetic diseases. Cf.:medical g.. epidemiologic g. the study of g. as a phenomenon of defined populations by the criteria, methods, and objectives of epidemiology rather than of population g.. galtonian g. the study of traits by analysis of the first two moments of metrical data; the preferred method for analysis of traits following the multivariate gaussian distribution. Galtonian-Fisher g. the g. of measurable traits determined by multiple loci which make contributions that are independent, additive, and approximately equal. SYN: multilocal g.. human g. the study of the genetic aspects of humans as a species. Cf.:medical g.. mathematical g. the study of genetic traits by formal analysis, e.g., quantitative g., population dynamics, genetic epidemiology, modeling. medical g. the study of the etiology, pathogenesis, and natural history of human diseases which are at least partially genetic in origin. Cf.:clinical g., human g.. mendelian g. the study of the pattern of segregation of phenotypes under the control of genetic loci taken one at a time. microbial g. the study of hereditary mechanisms of microbes. modern g. that body of method and analysis that perceives g. as the study of the economy of nucleic acids and associated compounds. molecular g. molecular biology applied to g.. multilocal g. SYN: Galtonian-Fisher g.. population g. the study of genetic influences on the components of cause and effect in the somatic characteristics of populations. quantitative g. the formal study of measurable genetic traits, traditionally but not necessarily confined to galtonian g.. reverse g. term referring to tracing of a gene responsible for a disease by learning its position in the human genome. This approach makes no claim of providing information about the gene product. SYN: positional cloning. somatic cell g. the study of the structure, organization, and function of a genome by the techniques of cell hybridization. statistical g. the study of the applications of principles of statistics to problems in g.. transplantation g. g. as applied to the transplanting of tissues from one animal to another.

genetotrophic (je-net-o-trof′ik)
Relating to inherited individual distinctions in nutritional requirements. [G. genesis, origin, + trophe, nourishment]

Geneva Convention
An international agreement formed at meetings in Geneva, Switzerland, in 1864 and 1906, relating (among medical subjects) to the safeguarding of the wounded in battle, of those having the care of them, and of the buildings in which they are being treated. The direct outcome of the first of these meetings was the establishment of the Red Cross Society.

Geneva lens measure
See under measure.

Octave, French bacteriologist, 1875–1957. See G. phenomenon, Bordet-G. potato blood agar, Bordet-G. bacillus, Bordet-G. phenomenon, Bordet and G. reaction.

genial, genian (je-ni′al, -ni′an)
SYN: mental (2) . [G. geneion, chin]

Producing, forming; produced, formed by. [G. genos, birth]

genicula (je-nik′u-la)
Plural of geniculum.

genicular (je-nik′u-lar)
Commonly used to mean genual.

geniculate (je-nik′u-lat)
1. Bent like a knee. SYN: geniculated. 2. Referring to the geniculum of the facial nerve, denoting the ganglion there present. 3. Denoting the lateral or medial g. body. [L. geniculo, pp. -atus, to bend the knee, fr. genu, knee]

geniculated (je-nik′u-la-ted)
SYN: geniculate (1) .

geniculum, pl .genicula (je-nik′u-lum, -la)
1. [TA] A small genu or angular kneelike structure. 2. A knotlike structure. [L. dim. of genu, knee] g. canalis facialis [TA] SYN: g. of facial canal. g. of facial canal [TA] the bend in the facial canal linking the medial and lateral crura of the horizontal port of the canal and corresponding to the location of the geniculate ganglion of the facial nerve. SYN: g. canalis facialis [TA] , genu of facial canal. g. of facial nerve [TA] 1. a sharp bend in the facial nerve in the facial canal where it turns posteriorly from its previously anterior course to run in the medial wall of the middle ear (external g.); 2. complex loop of facial nerve fibers around the abducens nucleus (internal g.). SYN: g. nervus facialis [TA] . g. nervus facialis [TA] SYN: g. of facial nerve.

Suffix used to denote the basic steroid unit of the toxic substance, usually a steroid glycoside ( e.g., the aglycon portion).

genioglossus (je′ni-o-glos′us)
SYN: g. (muscle). [G. geneion, chin, + glossa, tongue]

geniohyoid (je-ni′o-hi′oyd)
SYN: g. (muscle).

geniohyoideus (je-ni′o-hi-oyd′e-us)
SYN: geniohyoid (muscle). [G. geneion, chin, + hyoeides, y-shaped, hyoid]

genion (je-ni′on)
The tip of the mental spine, a point in craniometry. [G. geneion, chin]

genioplasty (je′ni-o-plas-te)
Surgical correction of the bony contour of the chin. [G. geneion, chin, cheek, + plastos, formed]

genital (jen′i-tal)
1. Relating to reproduction or generation. 2. Relating to the primary female or male sex organs or genitals. 3. Relating to or characterized by genitality. [L. genitalis, pertaining to reproduction, fr. gigno, to bring forth]

genitalia (jen′i-ta′le-a) [TA]
The organs of reproduction or generation, external and internal. SYN: organa g. [TA] , genital organs, genitals. [L. neut. pl. of genitalis, genital] ambiguous g. SYN: genital ambiguity. ambiguous external g. SYN: genital ambiguity. external g. the vulva in the female, and the penis and scrotum in the male. female external g. [TA] the external feminine genital organs, the vulva and clitoris. SYN: external female genital organs, organa g. feminina externa. female internal g. [TA] the internal feminine genital organs, the ovaries, uterine tubes, uterus, and vagina. SYN: internal female genital organs, organa g. feminina interna. indifferent g. reproductive organs of the embryo before definitive sex formation. male external g. [TA] the external masculine genital organs, the penis and scrotum. SYN: external male genital organs, organa g. masculina externa. male internal g. [TA] the internal masculine genital organs, the testes, epididymides, deferent ducts, seminal vesicles, prostate, and bulbourethral glands. SYN: internal male genital organs, organa g. masculina interna.

genitality (jen-i-tal′i-te)
In psychoanalysis, a term referring to the genital components of sexuality ( i.e., the penis and vagina), as opposed, for example, to orality and anality.


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