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Filebox - Biotechnology Dictionary Category: Earth and Environment > Biotechnology Date & country: 13/09/2007, USA Words: 455

DNA polymerase
See Polymerase.

DNA polymorphism
One of two or more alternate forms (alleles) of a chromosomal locus that differ in nucleotide sequence or have variable numbers of repeated nucleotide units. (See Allele.)

DNA sequencing
Procedures for determining the nucleotide sequence of a DNA fragment.

DNase (deoxyribonuclease)
See Nuclease.

Dominant
An allele is said to be dominant if it expresses its phenotype even in the presence of a recessive allele. See Allele, Phenotype, Recessive.

Dominant gene
A gene whose phenotype is when it is present in a single copy.

Dominant(-acting) oncogene
A gene that stimulates cell proliferation and contributes to oncogenesis when present in a single copy. (See Oncogene.)

Dormancy
A period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability.

Double helix
Describes the coiling of the antiparallel strands of the DNA molecule, resembling a spiral staircase in which the paired bases form the steps and the sugar-phosphate backbones form the rails.

Downstream
The region extending in a 3' direction from a gene.

dscDNA
See double-stranded complementary DNA.

Duplex DNA
Double-stranded DNA.

Ecology
The study of the interactions of organisms with their environment and with each other.

Ecosystem
The organisms in a plant population and the biotic and abiotic factors which impact on them. See abiotic factors; Biotic factors.

Electrophoresis
The technique of separating charged mol- ecules in a matrix to which is applied an electrical field. (See Agarose gell electrophoresis, Polycrylamide gell electrophoresis.)

Electroporation
A method for transforrning DNA, especially useful for plant cells, in which high voltage pulses of electricity are used to open pores in cell membranes, through which foreign DNA can pass.

Encapsidation
Process by which a virus' nucleic acid is enclosed in a capsid. See Coat protein.

Endonuclease
See Nuclease.

Endophyte
An organism that lives inside another.

Enzymes
Proteins that control the various steps in all chemical reactions.

EPA
See Environmental Protection Agency.

Escherichia coli
A commensal bacterium inhabiting the human colon that is widely used in biology, both as a simple model of cell biochemical function and as a host for molecular cloning experiments.

Ethidium bromide
A fluorescent dye used to stain DNA and RNA. The dye fluoresces when exposed to UV light.

Eukaryote
An organism whose cells possess a nucleus and other membrane-bound vesicles, including all members of the protist, fungi, plant and animal kingdoms; and excluding viruses, bacteria, and blue-green algae. See Prokaryote.

Evolution
The long-term process through which a population of organisms accumulats genetic changes that enable its members to successfully adapt to environmental conditions and to better exploit food resources.

Exon
A DNA sequence that is ultimately translated into protein. See DNA.

Exonuclease
See Nuclease.

Express
To translate a gene's message into a molecular product.

Expression library
(See Library.)

FDA
See Food and Drug Administration.

Federal Plant Pest Act (PPA)
See U.S. Department of Agriculture.

Federal Seed Act
See U.S. Department of Agriculture.

FIFRA
The Federal Insecticide, Fungicide, and Rodenticide Act. See Environmental Protection Agency.

Flanking region
The DNA sequences extending on either side of a specific locus or gene.

Food and Drug Administration (FDA)
The U.S. agency responsible for regulation of biotechnology food products. The major laws under which the agency has regulatory powers include the Food, Drug, and Cosmetic Act; and the Public Health Service Act.

Food, Drug, and Cosmetic Act
See Food and Drug Administration.

Fungicide
An agent, such as a chemical, that kills fungi.

Fungus
A microorganism that lacks chlorophyll.

Fusion gene
A hybrid gene created by joining portions of two different genes (to produce a new protein) or by joining a gene to a different promoter (to alter or regulate gene transcription).

Gamete
A haploid sex cell, egg or sperm, that contains a single copy of each chromosome.

GEM
A genetically engineered microorganism.

Gene
A locus on a chromosome that encodes a specific protein or several related proteins. It is considered the functional unit of heredity. (See Dominant gene, Fusion gene, Gene amplification, Gene expression, Gene flow, Gene pool, Gene splicing, Gene translocation, Recessive gene, Regulatory gene.)

Gene amplification
The presence of multiple genes. Amplification is one mechanism through which proto-oncogenes are activated in malignant cells.

Gene cloning
The process of synthesizing multiple copies of a particular DNA sequence using a bacteria cell or another organism as a host. See DNA, Host.

Gene expression
The process of producing a protein from its DNA- and mRNA-coding sequences.

Gene flow
The exchange of genes between different but (usually) related populations.

Gene frequency
The percentage of a given allele in a population of organisms. See Allele.

Gene insertion
The addition of one or more copies of a normal gene into a defective chromosome.

Gene linkage
The hereditary association of genes located on the same chromosome.

Gene modification
The chemical repair of a gene's defective DNA sequence. See DNA.

Gene pool
The totality of all alleles of all genes of all individuals in a particular population.

Gene splicing
Combining genes from different organisms into one organism. See recombinant DNA.

Gene translocation
The movement of a gene fragment from one chromosomal location to another, which often alters or abolishes expression.

Genetic assimilation
Eventual extinction of a natural species as massive pollen flow occurs from another related species and the older crop becomes more like the new crop. See Gene flow.

Genetic code
The three-letter code that translates nucleic acid sequence into protein sequence. The relationships between the nucleotide base-pair triplets of a messenger RNA molecule and the 20 amino acids that are the building blocks of proteins. See Base pair, Nucleic acid, Nucleotide.

Genetic disease
A disease that has its origin in changes to the genetic material, DNA. Usually refers to diseases that are inherited in a Mendelian fashion, although noninherited forms of cancer also result from DNA mutation.

Genetic drift
Random variation in gene frequency from one generation to another.

Genetic engineering
The manipulation of an organism's genetic endowment by introducing or eliminating specific genes through modern molecular biology techniques. A broad definition of genetic engineering also includes selective breeding and other means of artificial selection.

Genetic linkage map
A linear map of the relative positions of genes along a chromosome. Distances are established by linkage analysis, which determines the frequency at which two gene loci become separated during chromosomal recombination. (See Mapping.)

Genetic marker
A gene or group of genes used to 'mark' or track the action of microbes.

Genome
The genetic complement contained in the chromosomes of a given organism, usually the haploid chromosome state.

Genomic library
A library composed of fragments of genomic DNA. (See Library.)

Genotype
The structure of DNA that determines the expression of a trait. See Phenotype.

Genus
A category including closely related species. Interbreeding between organisms within the same category can occur.

GEO
Genetically engineered organism.

Germ cell
Reproductive cell. See Somatic cell.

Germ cell (germ line) gene therapy
The repair or re- placement of a defective gene within the gamete-forming tissues, which produces a heritable change in an organism's genetic constitution.

GMO
Genetically modified organism.

Green revolution
Advances in genetics, petrochemicals, and machinery that culminated in a dramatic increase in crop productivity during the third quarter of the 20th century.

Growth curve
See Growth phase.

Growth factor
A serum protein that stimulates cell division when it binds to its cell-surface receptor.

Growth phase (curve)
The characteristic periods in the growth of a bacterial culture, as indicated by the shape of a graph of viable cell number versus time. (See Death phase, Lag phase, Logarithmic phase, Stationary phase.)

Haploid cell
A cell containing only one set, or half the usual (diploid) number, of chromosomes.

Hemophilia
An X-linked recessive genetic disease, caused by a mutation in the gene for clotting factor VIII (hemophilia A) or clotting factor IX (hemophilia B), which leads to abnormal blood clotting.

Herbicide
Any substance that is toxic to plants; usually used to kill specific unwanted plants.

Heterochromatin
Dark-stained regions of chromosomes thought to be for the most part genetically inactive.

Heteroduplex
A double-stranded DNA molecule or DNA-RNA hybrid, where each strand is of a different origin.

Heterogeneous nuclear RNA (hnRNA)
The name originally given to large RNA molecules found in the nucleus, which are now known to be unedited mRNA transcripts, or pre-mRNAs. (See RNA.)

HGH
See Human growth hormone.

hnRNA
See Heterogeneous nuclear RNA.

Homologous chromosomes
Chromosomes that have the same linear arrangement of genes--a pair of matching chromosomes in a diploid organism. See Chromosomes.

Homologous recombination
The exchange of DNA fragments between two DNA molecules or chromatids of paired chromosomes (during crossing over) at the site of identical nucleotide sequences.

Homozygote
An organism whose genotype is characterized by two identical alleles of a gene. See Allele, Genotype.

Host
An organism that contains another organism.

Human Genome Project
A project coordinated by the National Institutes of Health (NIH) and the Department of Energy (DOE) to determine the entire nucleotide sequence of the human chromosomes. (See NIH.)

Hybrid
The offspring of two parents differing in at least one genetic characteristic (trait). Also, a heteroduplex DNA or DNA-RNA molecule.

Hybridization
The hydrogen bonding of complementary DNA and/or RNA sequences to form a duplex molecule. (See Northern hybridization, Southern hybridization.)

Hybridoma
A hybrid cell, composed of a B Iymphocyte fused to a tumor cell, which grows indefinitely in tissue culture and is selected for the secretion of a specific antibody of interest.

Hydrogen bond
A relatively weak bond formed between a hydrogen atom (which is covalently bound to a nitrogen or oxygen atom) and a nitrogen or oxygen with an unshared electron pair.

Hydrolysis
A reaction in which a molecule of water is added at the site of cleavage of a molecule to two products.

Immortalizing oncogene
A gene that upon transfection enables a primary cell to grow indefinitely in culture. (See Oncogene.)

In situ
Refers to performing assays or manipulations with intact tissues.

In vivo
Refers to biological processes that take place within a living organism or cell.

Incomplete dominance
A condition where a heterozygous off- spring has a phenotype that is distinctly different from, and intermediate to, the parental phenotypes. See Heterozygote, Phenotype.

Initiation codon
The mRNA sequence AUG, coding for methionine, which initiates translation of mRNA.

Inositol lipid
A membrane-anchored phospholipid that transduces hormonal signals by stimulating the release of any of several chemical messengers. (See Phospholipid.)

Insertion mutations
Changes in the base sequence of a DNA molecule resulting from the random integration of DNA from another source. See DNA, Mutation.

Insulin
A peptide hormone secreted by the islets of Langerhans of the pancreas that regulates the level of sugar in the blood.

Interferon
A family of small proteins that stimulate viral resistance in cells.

Intergenic regions
DNA sequences located between genes that comprise a large percentage of the human genome with no known function.