structural gene


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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.
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.

struc·tur·al gene

a gene that codes for a specific protein or peptide.

structural gene

n.
A gene that encodes the amino acid sequence of a protein.

structural gene

a gene that specifies the amino acid sequence of a polypeptide.

struc·tur·al gene

(strŭk'shŭr-ăl jēn)
A gene that codes for a specific protein or peptide.

structural gene

A GENE that codes, as most do, for the amino acid sequence of a protein rather than for a regulatory protein.

structural gene

see OPERON MODEL.

gene

the unit of heredity most simply defined as a specific segment of DNA, usually in the order of 1000 nucleotides, that specifies a single polypeptide. Many phenotypic characteristics are determined by a single gene, while others are multigenic. Genes are specifically located in linear order along the single DNA molecule that makes up each chromosome. All eukaryotic cells contain a diploid (2n) set of chromosomes so that two copies of each gene, one derived from each parent, are present in each cell; the two copies often specify a different phenotype, i.e. the polypeptide will have a somewhat different amino acid composition. These alternative forms of gene, both within and between individuals, are called alleles. Genes determine the physical (structural genes), the biochemical (enzymes), physiological and behavioral characteristics of an animal.
The formation of gametes (sperm, ova) involves a process of meiosis, which allows crossing over between four pairs of chromosomes, two derived from each parent, which means that new forms of a particular chromosome are created. Gamete formation also results in cells (gametes) with a haploid (n) set of chromosomes that in fertilization creates a new individual, which is a recombinant of 2n chromosomes, half derived by way of the ovum from the mother and half via the spermatozoa from the father.
Changes in the nucleotide sequence of a gene, either by substitution of a different nucleotide or by deletion or insertion of other nucleotides, constitute mutations which add to the diversity of animal species by creating different alleles and can be used as a basis for genetic selection of different phenotypes. Some mutations, be they a single base change in a single gene or a major deletion, are lethal.

gene action
the way in which genes exert their effects on tissues or processes, e.g. by being dominant or recessive, or partially so, being absent, being sex-linked, being involved in chromosomal aberrations.
allelic g's
different forms of a particular gene usually situated at the same position (locus) in a pair of chromosomes.
gene amplification
see gene duplication (below).
gene bank
the collection of DNA sequences in a given genome. Called also gene library.
barring gene
responsible for the barred pattern on the feathers of Barred Plymouth Rock birds.
gene box
see box (4).
gene clone
see clone.
gene cluster
a group of related genes derived from a common ancestral gene, located closely together on the same chromosome. Called also multigene family.
complementary g's
two independent pairs of nonallelic genes, neither of which is functional without the other.
gene conversion
a non-reciprocal exchange of DNA elements during meiosis which results in a functional rearrangement of chromosomal DNA.
dhfr gene
dihydrofolate reductase gene; an enzyme required to maintain cellular concentrations of H2 folate for nucleotide biosynthesis, and which has been used as a 'selective marker'; cells lacking the enzyme only survive in media containing thymidine, glycine and purines; mutant cells (dhfr) transfected with DNA that is dhfr′ can be selectively grown in medium lacking these elements.
diversity (D) gene
genes located in diversity (D) segment; contribute to the hypervariable region of immunoglobulins.
dominant gene
one that produces an effect (the phenotype) in the organism regardless of the state of the corresponding allele. Examples of traits determined by dominant genes are short hair in cats and black coat color in dogs.
gene duplication
as a result of non-homologous recombination, a chromosome carries two or more copies of a gene.
gene expression
gene frequency
the proportion of the substances or animals in the group which carry a particular gene.
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 (MHC) that govern the immune response to individual immunogens.
jumping gene
see mobile dna.
gene knockout
replacement of a normal gene with a mutant allele, as in gene knockout mice.
lethal gene
one whose presence brings about the death of the organism or permits survival only under certain conditions.
gene library
see gene bank (above).
gene locus
see locus.
mutant gene
one that has undergone a detectable mutation.
non-protein encoding gene
the final products of some genes are RNA molecules rather than proteins.
overlapping g's
when more than one mRNA is transcribed from the same DNA sequence; the mRNAs may be in the same reading frame but of different size or they may be in different reading frames.
gene pool
total of all genes possessed by all members of the population which are capable of reproducing during their lifetime.
gene probe
see probe (2).
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.
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.
reporter gene
one that produces products which can be measured and therefore used as an indicator of whether a DNA construct has successfully been transferred.
sex-linked gene
one that is carried on a sex chromosome, especially an X chromosome.
gene splicing
structural gene
nucleotide sequences coding for proteins.
gene therapy
the insertion of functional genes into cells of the host in order to alter its phenotype, usually used to treat an inherited defect.
gene transcription
gene transfer
tumor suppressor g's
a class of genes that encode proteins that normally suppress cell division that when mutated allow cells to continue unrestricted cell division and may result in a tumor.
References in periodicals archive ?
The differences in pigmentation between brown green and white cotton fiber can be mined by the molecular study of structural genes of flavonoid biosynthesis pathway.
A PCR array provided quick amplification and sequence identity of the various structural genes to determine if these bacteriocins were previously studied.
Suggested roles for transposable elements have included the regulation of structural genes (McClintock 1956) and the generation of genetic or chromosomal variation (Nevers and Saedler 1977).
1996) had BA QTLs in mid-chromosome 4, medial to the area found in S/M, and overlapping the Bmy1 structural gene.
These findings suggest that different structural genes may be under the control of identical regulatory systems and that nucleotide substitutions in AmpD could lead to the stable co-expression of the NmcA together with overexpression of the AmpC enzyme in E.
Restricted structural gene polymorphism in the Mycobacterium tuberculosis complex indicates evolutionarily recent global dissemination.
The experts analysed the structural genes E1 and E2 in the chikungunya virus.
While it has long been known that some traits such as antibiotic resistance can be shared between different types of pathogen, mapping the evolutionary histories of sequences has revealed that all manner of biochemical and structural genes can be passed back and forth.
Genomics is the study of all of the nucleotide sequences, including structural genes, regulatory sequences, and noncoding DNA segments, in the chromosomes of an organism.
Genetic variability of Yersinia pestis isolates as predicted by PCR-based IS100 genotyping and analysis of structural genes encoding glycerol-3-phosphate dehydrogenase (glpD).
Similarly, Salinas and Benito (1984) investigated chromosomal locations of structural genes of PRX enzymes in rye and they stated that PRX enzymes produced band formation in both poles.
In turn, molecular analysis of structural genes and their functional regulation and expression often lead to crucial knowledge of components of metabolic pathways of various economic traits.

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