Gene

gene

 [jēn]

one of the biologic units of heredity, self-reproducing, and located at a definite position (locus) on a particular chromosome. Genes make up segments of the complex deoxyribonucleic acid (DNA) molecule that controls cellular reproduction and function. There are thousands of genes in the chromosomes of each cell nucleus; they play an important role in heredity because they control the individual physical, biochemical, and physiologic traits inherited by offspring from their parents. Through the genetic code of DNA they also control the day-to-day functions and reproduction of all cells in the body. For example, the genes control the synthesis of structural proteins and also the enzymes that regulate various chemical reactions that take place in a cell.

The gene is capable of replication. When a cell multiplies by mitosis each daughter cell carries a set of genes that is an exact replica of that of the parent cell. This characteristic of replication explains how genes can carry hereditary traits through successive generations without change.

allelic gene allele.

complementary g's two independent pairs of nonallelic genes, neither of which will produce its effect in the absence of the other.

DCC gene (deleted in colorectal carcinoma) a gene normally expressed in the mucosa of the colon but reduced or absent in a small proportion of patients with colorectal cancer.

dominant gene one that produces an effect (the phenotype) in the organism regardless of the state of the corresponding allele. An example of a trait determined by a dominant gene is brown eye color. See also heredity.

histocompatibility gene one that determines the specificity of tissue antigenicity (hla antigens) and thus the compatibility of donor and recipient in tissue transplantation and blood transfusion.

holandric g's genes located on the Y chromosome and appearing only in male offspring.

immune response (Ir) g's genes of the major histocompatibility complex that govern the immune response to individual immunogens.

immune suppressor (Is) g's genes that govern the formation of suppressor T lymphocytes.

immunoglobulin g's the genes coding for immunoglobulin heavy and light chains, which are organized in three loci coding for κ light chains, λ light chains, and heavy chains.

K-ras gene a type of oncogene.

lethal gene one whose presence brings about the death of the organism or permits survival only under certain conditions.

major gene a gene whose effect on the phenotype is always evident, regardless of how this effect is modified by other genes.

mutant gene one that has undergone a detectable mutation.

operator gene one serving as a starting point for reading the genetic code, and which, through interaction with a repressor, controls the activity of structural genes associated with it in the operon.

gene pool all of the genes possessed by all of the members of a population that will reproduce.

recessive gene one that produces an effect in the organism only when it is transmitted by both parents, i.e., only when the individual is homozygous. See also heredity.

regulator gene (repressor gene) one that synthesizes repressor, a substance which, through interaction with the operator gene, switches off the activity of the structural genes associated with it in the operon.

sex-linked gene a gene carried on a sex chromosome (X or Y); only X linkage has clinical significance. See X-linked gene.

gene splicing recombinant dna technology.

structural gene one that forms templates for messenger RNA and is thereby responsible for the amino acid sequence of specific polypeptides.

tumor suppressor gene a gene whose function is to limit cell proliferation and loss of whose function leads to cell transformation and tumor growth; called also antioncogene.

X-linked gene a gene carried on the X chromosome; the corresponding trait, whether dominant or recessive, is always expressed in males, who have only one X chromosome. the term “X-linked” is sometimes used synonymously with “sex-linked,” since no genetic disorders have as yet been associated with genes on the Y chromosome.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

gene

(jēn), According to the standards of the International System for Human Genome Nomenclature (ISGN), a human gene symbol should be 2-9 characters in length, may include Arabic numerals as well as Roman letters but must begin with a letter, and is printed with all letters capitalized and in italic type. It may not include superscripts, subscripts, Greek letters, Roman numerals, or punctuation. The symbol must be unique and should be an abbreviation of the full gene name. Thus, α-fetoprotein, AFP; antithrombin III, AT3.

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 gene 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 gene 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, genes 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.

Synonym(s): factor (3)

[G. genos, birth]

Farlex Partner Medical Dictionary © Farlex 2012

gene

(jēn)

n.

A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and is transcribed into an RNA molecule that may function directly or be translated into an amino acid chain. Genes undergo mutation when their DNA sequences change.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

gene

Genetics Classic mendelian definition A unit of inheritance carrying a single trait and recognized by its ability to mutate and undergo recombination–this definition is widely recognized as primitive Current definition A segment of DNA nucleotides, comprised of 70 to 30,000 bp including introns, that encodes a sequence of mRNA, capable of giving rise to a functional producte–eg, enzyme, hormone, receptor–polypeptide; genes may be structural, and form cell components, or functional, and have a regulatory role; a biological unit of heredity which is self-reproducing and located at a definite position on a particular chromosome; genes are working subunits of DNA; each of the body's 50,000 to 100,000 genes contains the code for a specific product, commonly for making a specific protein–eg an enzyme; the functional and physical unit of heredity passed from parent to offspring. See Cellular oncogene, Crime gene, Expressed gene, Functional gene, Housekeeping gene, Lethal gene, Mutable gene, Mutator gene, Pseudogene, Reporter gene, Structural gene, Suppressor gene, Tumor suppressor. Cf Chromosome.

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

gene

(jēn)

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 gene 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 gene 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, genes 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.
Synonym(s): factor (3) .

[G. genos, birth]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

gene

(jen) [Ger. Gen, ult. fr Gr. genos, kind, race, descent]

AUTOSOMAL DOMINANT INHERITANCE

AUTOSOMAL DOMINANT INHERITANCE

The basic unit of heredity, made of DNA, the code for a specific protein. Each gene occupies a certain location on a chromosome. Genes are self-replicating sequences of DNA nucleotides, subject to random structural changes (mutations). Hereditary traits are controlled by pairs of genes in the same position on a pair of chromosomes. These alleles may be either dominant or recessive. When both pairs of an allele are either dominant or recessive, the individual is said to be homozygous for the traits coded by the gene. If the alleles differ (one dominant and one recessive), the individual is heterozygous. See: illustration; chromosome; DNA; RNA

autosomal dominant gene

A dominant gene that is found on any chromosome other than the X or Y chromosome.

autosomal recessive gene

A recessive gene that is found on any chromosome other than the X or Y chromosome.

BRCA1 gene

A breast cancer gene found in a small percentage of patients with this malignancy, and carried by some individuals who will develop breast cancer later in life.

Patient care

BRCA1 Gene Mutation: Patient care focuses on determining the family history of the patient and referral to a genetic counselor with expertise in this mutation when appropriate.

BRCA2 gene

A breast cancer gene found in a small number of patients with breast and ovarian cancers, and carried by some individuals who will develop breast cancer later in life.

complementary genes

Nonallelic, independently located genes, neither of which will be expressed in the absence of the other.

cystic fibrosis transmembrane conductance regulator gene

The gene that codes for a protein that regulates the movement of ions, esp. chloride, across cell membranes.

dominant gene

See: dominant

histocompatibility gene

One of the genes composing the HLA complex that determines the histocompatibility antigenic markers on all nucleated cells. These genes create the antigens by which the immune system recognizes “self” and determines the “nonself” nature of pathogens and other foreign antigens. These antigens are crucial determinants of the success or failure of organ transplantation.

See: histocompatibility locus antigen

holandric gene

A gene located in the nonhomologous portion of the Y chromosome of males.

homeobox gene

Any transcription factor that regulates the growth, differentiation, replication, and movement of cells in the body. These genes influence both normal and abnormal embyological development and the development or suppression of malignant tumors.

housekeeping gene

A gene expressed in nearly every cell and every tissue of an organism, i.e., one that encodes a protein fundamental to cellular activity throughout the organism.

immune response gene

One of the many genes that control the ability of leukocytes to respond to specific antigens.

See: antigen; B cell; HLA complex; T cell

inhibiting gene

A gene that prevents the expression of another gene.

interleukin-28B gene

A genetic variant that increases the likelihood of having a favorable to response to antiviral treatment for chronic hepatitis C, genotype 1 infection (traditionally the most resistant hepatitis C genotype).

lethal gene

A gene that creates a condition incompatible with life and usually results in the death of the fetus.

modifying gene

A gene that influences or alters the expression of other genes.

mutant gene

An altered gene that permanently functions differently than it did before its alteration.

operator gene

A gene that controls the expression of other genes.

See: operon

gene p53

A gene thought to be important in controlling the cell cycle, DNA repair and synthesis, and programmed cell death (apoptosis). Mutations of p53 have occurred in almost half of all types of cancer, arising from a variety of tissues. Mutant types may promote cancer. The normal, wild-type gene produces a protein important in tumor suppression.

pleiotropic gene

A gene that has multiple effects.

posttranscriptional gene silencing

RNA interference.

presenilin gene

Rare traits responsible for early-onset Alzheimer's disease.

RB gene

Tumor suppressor gene encoding for the retinoblastoma (RB) protein, mutations of which are associated with various human tumors, including retinoblastoma, osteosarcoma, some leukemias, and some adenocarcinomas.

See: tumor suppressor gene; retinoblastoma

recessive gene

A trait that is not expressed unless it is present in the genes received from both parents. A recessive trait may be apparent in the phenotype only if both alleles are recessive.

Synonym: recessive characteristic

regulator gene

A gene that can control some specific activity of another gene.

sex-linked gene

Sex-linked characteristic.

structural gene

A gene that determines the structure of polypeptide chains by controlling the sequence of amino acids.

susceptibility gene

A gene that increases a person's likelihood of contracting a heritable illness.

tumor suppressor gene

A gene that suppresses the growth of malignant cells.

See: cancer

X-linked gene

A gene on the X chromosome for which there is no corresponding gene on the Y chromosome. X-linked genes (e.g., the gene for red-green color blindness) are expressed but in males even these genes are recessive because there is no correponding gene to dominate them.

Medical Dictionary, © 2009 Farlex and Partners

gene

The physical unit of heredity, represented as a continuous sequence of bases, arranged in a code, in groups of three (codons), along the length of a DNA molecule (nucleic acid). The gene is the transcription code for a sequence of AMINO ACIDS linked to form a single POLYPEPTIDE chain and includes lengths on either side of the coding region known as the leader and the trailer, and non-coding sequences (INTRONS) that intervene between the coding segments. The latter are called EXONS. Exons tend to be conserved throughout a long evolutionary period; introns may vary considerably in length. The length of a gene is largely determined by the introns. The function of genes can be altered by changes (MUTATIONS) in the base sequences and their operation is regulated by adjacent, or even remote, parts of the DNA molecule. All genes are present in all nucleated cells, but only genes relevant to the particular cell are ‘switched on’ as required.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

gene

the fundamental physical unit of heredity that transmits information from one cell to another and hence one generation to another. Genes consist of specific sequences of DNA nucleotides which can code for the structure of polypeptide chains (see CISTRON), tRNA molecules and rRNA molecules (see TRANSCRIPTION, TRANSLATION). Individual genes can be recognized through the existence of variable forms, or ALLELES, that form the basis of GENETIC VARIABILITY. Organisms can be considered as gene carriers, being controlled by genes in such a way as to maximize the chances of survival of the genetic material.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Gene

A building block of inheritance, which contains the instructions for the production of a particular protein, and is made up of a molecular sequence found on a section of DNA. Each gene is found on a precise location on a chromosome.

Mentioned in: Acoustic Neuroma, Albinism, Birth Defects, Blood Typing and Crossmatching, Cutis Laxa, Familial Polyposis, Gene Therapy, Genetic Testing, Periodic Paralysis, Phenylketonuria, Polydactyly and Syndactyly, Porphyrias, Prader-Willi Syndrome, Pseudoxanthoma Elasticum, Retinoblastoma, Situs Inversus, Von Willebrand Disease, Wilson Disease, Wiskott-Aldrich Syndrome

Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

gene

The unit of heredity which determines, or contributes to, one inherited feature of an organism (e.g. eye colour). Physically, a gene is composed of a defined DNA sequence, located at a specific place (locus) along the length of a chromosome and transmitted by a parent to its offspring. The DNA sequence of nucleotide bases (adenine, cytosine, guanine and thymine) encodes a specific sequence of amino acids corresponding to a particular protein. If the DNA sequence at one locus is identical on a pair of homologous chromosomes the organism is referred to as homozygous (homozygote) and if the DNA sequence is not identical it is referred to as heterozygous (heterozygote). The total effect of all genes influences the development and functioning of all organs and systems in the body. See chromosome; genome; inheritance; mutation; pedigree.

Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

gene

(jēn)

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.
Synonym(s): factor (3) .

[G. genos, birth]

Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about Gene

Q. What Is the BRCA Gene? We have a history of breast cancer in our family and my doctor advised me to get genetic testing for the BRCA gene. How is this gene related to breast cancer?

A. BRCA1 (breast cancer 1, early onset) is a human gene that belongs to a class of genes known as tumor suppressors, which maintains gene integrity to prevent uncontrolled proliferation (what causes cancer cells to develop). Variations in the gene have been implicated in a number of hereditary cancers, mainly breast, ovarian and prostate. The BRCA family of genes are known today to give a significant increased risk for breast cancer in families. A women should be tested if a number of women in her family have had breast cancer throughout their life, especially at a young age.

Q. How can genes cause breast cancer? We say genetics play a role in breast cancer but how is that possible …………I mean how can genes cause breast cancer?

A. Genes are the chemical entities and they can be changed of their set of structure inside a cell, when is exposed to radiation or any chemical through toxic food. Some genes like BRCA1 & 2 expanded as Breast Cancer 1 & 2 are helpful to prevent any cancer development of a single cell. These genes act as guards who prevent a cell to become cancerous. When anyone inherits this gene from parents and if they are defected they are also prone to breast cancer.

Q. can diet control breast cancer if the gene is supposed to be the cause of breast cancer?

A. No…I am sorry, it can`t. If it is radiation then diet cannot control. When we have exposure to toxic food and non toxic food where the free radical production is high, the free radical production can be controlled with the consumption of antioxidant rich food. Well it’s only a preventive step for the free radical rich food and not for the radiation induced cancer. Breast cancer is only treated with surgery and therapies. Diet plays a good role when your treatment is on, as it gives strength and overall wellbeing.

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