Canadian Medical Guide > Biological Sciences > Genetic Structures > Genes Terms and Definitions

Genes

Medical Definition:	Specific sequences of nucleotides along a molecule of DNA (or, in the case of some viruses, RNA) which represent the functional units of HEREDITY. The majority of eukaryotic genes contain coding regions (CODONS) that are interrupted by non-coding regions (INTRONS) and are therefore labeled split genes.
Guide Notes:	locus = CHROMOSOME MAPPING; flow = GENETICS, POPULATION; interaction = PHENOTYPE; suppressor genes = GENES, SUPPRESSOR; restorer genes: index under SUPPRESSION, GENETIC; repressor genes = GENES, REGULATOR; lac gene = LAC OPERON but consider also LAC FACTO
Also Called:	Genetic Materials,Split Genes

Genes Categories.

	Alleles - Mutually exclusive forms of the same gene, occupying the same locus on homologous chromosomes, and governing the same biochemical and developmental process.
	Genes, Archaeal - The genetic material of archaea.
	Genes, Bacterial - The genetic material of bacteria.
	Genes, cdc - Genes that code for proteins that regulate the CELL DIVISION CYCLE. These genes form a regulatory network that culminates in the onset of MITOSIS by activating the p34cdc2 protein (PROTEIN P34CDC2).
	Genes, Duplicate - Two identical genes showing the same phenotypic action but localized in different regions of a chromosome or on different chromosomes. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)
	Genes, Essential - Those genes found in an organism which are necessary for its viability and normal function.
	Genes, Fungal - The genetic material of fungi. It includes mating type genes of SACCHAROMYCES CEREVISIAE.
	Genes, Helminth - The hereditary material of helminths.
	Genes, Homeobox - Highly conserved DNA sequences which have been identified in specific gene transcripts ranging from those of Drosophila melanogaster to mouse and human. Homeobox genes function, in part, to generate DNA-binding proteins with an evolutionary conserved approximately 60-residue sequence (HOMEODOMAIN PROTEINS).
	Genes, Immediate-Early - Genes that show rapid and transient expression in the absence of de novo protein synthesis. The term was originally used exclusively for viral genes where immediate-early referred to transcription immediately following virus integration into the host cell. It is also used to describe cellular genes which are expressed immediately after resting cells are stimulated by extracellular signals such as growth factors and neurotransmitters.
	Genes, Insect - The hereditary material of insects.
	Genes, Lethal - Genes which result in the premature death of the organism; dominant lethal genes kill heterozygotes, whereas recessive lethal genes kill only homozygotes.
	Genes, MDR - Genes responsible for multidrug resistance resulting from their overexpression in mammalian cells. Mammalian P-glycoproteins are encoded by small MDR gene familes. The human multidrug resistance 1 (MDR1) gene responds to environmental stress including various anticancer agents. It is a major determinant in the development of resistance to a large number of cancer chemotherapeutic agents. (Biochem Biophys Res Commun 1994;199(3):1428-35; Cancer Res 1994:54(6):1536-41)
	Genes, Overlapping - Genes whose nucleotide sequences overlap to some degree. The overlapped sequences may involve structural or regulatory genes of eukaryotic or prokaryotic cells.
	Genes, Plant - The hereditary material of plants.
	Genes, Protozoan - The genetic material of protozoa.
	Genes, RAG-1 - Genes involved in activating the enzyme VDJ recombinase. RAG-1 is located on chromosome 11 in humans (chromosome 2 in mice) and is expressed exclusively in maturing lymphocytes.
	Genes, Regulator - Genes which regulate or circumscribe the activity of other genes; specifically, genes which code for proteins (repressors or activators) which regulate the genetic transcription of the structural genes and/or regulatory genes.
	Genes, Reporter - Genes whose expression is easily detectable and therefore used to study promoter activity at many positions in a target genome. In recombinant DNA technology, these genes may be attached to a promoter region of interest.
	Genes, sry - The primary testis-determining gene in mammalians, located on the Y CHROMOSOME. It codes for a high mobility group box transcription factor (TRANSCRIPTION FACTORS) which initiates the development of the TESTES from the embryonic GONADS.
	Genes, Structural - Genes that code for proteins required for the enzymatic and structural functions of cells. They include developmental and differentiated genes.
	Genes, Suppressor - Genes that have a suppressor allele or suppressor mutation (SUPPRESSION, GENETIC) which cancels the effect of a previous mutation, enabling the wild-type phenotype to be maintained or partially restored.
	Genes, Synthetic - Biologically functional sequences of DNA chemically synthesized in vitro.
	Genes, T-Cell Receptor - DNA sequences, in cells of the T-lymphocyte lineage, that code for T-cell receptors. The TcR genes are formed by somatic rearrangement (see GENE REARRANGEMENT, T-LYMPHOCYTE and its children) of germline gene segments, and resemble Ig genes in their mechanisms of diversity generation and expression.
	Genes, Viral - The hereditary material of viruses, consisting in all DNA and some RNA viruses of a single molecule of nucleic acid, and in some RNA viruses of several separate pieces of RNA.
	Multigene Family - A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)
	Oncogenes - Genes which can potentially induce neoplastic transformation. They include genes for growth factors, growth factor receptors, protein kinases, signal transducers, nuclear phosphoproteins, and transcription factors. When these genes are constitutively expressed after structural and/or regulatory changes, uncontrolled cell proliferation may result. Viral oncogenes have prefix "v-" before the gene symbol; cellular oncogenes (PROTO-ONCOGENES) have the prefix "c-" before the gene symbol.
	Open Reading Frames - Reading frames where successive nucleotide triplets can be read as codons specifying amino acids and where the sequence of these triplets is not interrupted by a STOP CODON.
	Pseudogenes - Genes bearing close resemblance to known genes at different loci, but rendered non-functional by additions or deletions in structure that prevent normal transcription or translation. When lacking introns and containing a poly-A segment near the downstream end (as a result of reverse copying from processed nuclear RNA into double-stranded DNA), they are called processed genes.
	Quantitative Trait Loci - Locations, on the GENOME, of GENES or other genetic elements that encode or control the expression of a QUANTITATIVE TRAIT.
	Transgenes - Genes that are introduced into an organism using GENE TRANSFER TECHNIQUES.

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