gene library

gene library.

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

see expression (3).

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

see 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

see transcription.

gene transfer

see recombination.

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.

gene library

Genomic library Genetics A molecular 'database' created when the mRNA extracted from a given tissue is reverse transcribed into cDNA (complementary DNA) segments, which in toto comprise the sequences of genes expressed in the tissue of interest. See Library Molecular biology A random collection of DNA fragments–typically representing the entire genome of an organism that have been inserted into a cloning vector.

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DNA library dominant gene gene gene amplification gene expression gene pool gene probe gene splicing gene therapy Gene transcription gene transfer jumping gene lethal gene mutant gene sex-linked gene structural gene			Astellas' decision to begin screening this target from Metabolex's gene library further underscores our expertise in understanding the molecular underpinnings of insulin resistance. ASTELLAS' SCREENING TRIGGERS MILESTONE PAYMENT TO METABOLEX by Worldwide Biotech Finally, the scientists located nine animals in Switzerland's Zurich Zoo that had come from the same area of eastern Madagascar as did the lemur that contributed the DNA sequence to the gene library. Out of the jungle: new lemurs found in Madagascar's forests by Moreira, N. / Science News Novozymes A/S (Bagsvaerd, Denmark) has patented a method of generating a gene library from an environmental pool of organisms, which gene library is enriched in DNA encoding a polypeptide with an activity of interest. Novozymes obtains United States patent by BIOTECH Patent News			gender dysphoria Gender Gap gender identity gender identity disorder Gender Map gender reassignment surgery gender role Gender Selection gender testing gender transposition Gender Verification gender-based illness gender-neutral gender-specific medicine gene gene amplification gene amplification technique gene augmentation therapy Gene Chip Gene Doping gene dosage compensation gene dose gene expression Gene Gun Gene Knockout Technique gene library gene map gene mapping gene marker gene pool gene probe gene product gene splicing gene testing gene therapy Gene transcription gene transfer gene-environment interaction gene-splicing genealogy genera general general adaptation syndrome general anatomy general anesthesia general anesthetic general duty nurse general health screen general immunity general paresis general practice			Gene Expression Pattern Scanner Gene expression programming Gene Expression Unit Gene families Gene family gene flow gene flow Gene for the GDP Gene frequencies Gene frequencies gene frequency gene frequency gene frequency Gene gun Gene Hackman Gene Hackman Gene Identification by NMD Gene interaction Gene interaction Gene interaction Gene Kelly Gene Kelly Gene knockdown Gene knockdown Gene knockdown Gene knockdown Gene knockout Gene knockout Gene knockout Gene Knockout Technique gene library Gene Lilly Surety Bonds, Inc. gene linkage gene linkage Gene locus Gene locus Gene locus gene loss Gene Loves Jezebel Gene Management Zone Gene manipulation Gene manipulation Gene manipulation Gene manipulation gene map gene map gene map gene map gene mapping gene marker Gene markers Gene markers Gene markers gene mutation gene mutation gene mutation gene mutation Gene of Interest Gene of Unknown Function Gene Ontology Gene Ontology Annotation Campaign