遗传学名词解释 英文版.doc

遗传学名词解释abortive transduction An event in which transducing DNA fails to be incorporated into the recipient chromosome. See transduction.accession number An identifying number or code assigned to a nucleotide or amino acid sequence for entry and cataloging in a database.acentric chromosome Chromosome or chromosome fragment with no centromere.acridine dyes A class of organic compounds that bind to DNA and intercalate into the double-stranded structure, producing local disruptions of base pairing. These disruptions result in nucleotide additions or deletions in the next round of replication.acrocentric chromosome Chromosome with the centromere located very close to one end. Human chromosomes 13, 14, 15, 21, and 22 are acrocentric.active site The substrate-binding site of an enzyme; in other proteins, the portion whose structural integrity is required for function.Adaptation A heritable component of the phenotype that confers an advantage in survival and reproductive success. The process by which organisms adapt to current environmental conditions.additive genes See polygenic inheritance.additive variance Genetic variance attributed to the substitution of one allele for another at a given locus. This variance can be used to predict the rate of response to phenotypic selection in quantitative traits.A-DNA An alternative form of right-handed, double-helical DNA. Its helix is more tightly coiled than the more common B-DNA, with 11 base pairs per full turn. In the A form, the bases in the helix are displaced laterally and tilted in relation to the longitudinal axis. It is not yet clear whether this form has biological significance. See B-DNA.albinism A condition caused by the lack of melanin production in the iris, hair, and skin. In humans, it is most often inherited as an autosomal recessive trait.Alkaptonuria An autosomal recessive condition in humans caused by lack of the enzyme homogentisic acid oxidase. Urine of homozygous individuals turns dark upon standing because of oxidation of excreted homogentisic acid. The cartilage of homozygous adults blackens from deposition of a pigment derived from homogentisic acid. Affected individuals often develop arthritic conditions.allele One of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects.allele-specific oligonucleotide (ASO)Synthetic nucleotides, usually 1520 bp in length, that under carefully controlled conditions will hybridize only to a perfectly matching complementary sequence.allelic exclusion In a plasma cell heterozygous for an immunoglobulin gene, the selective action of only one allele.allelism test See complementation test.allolactose A lactose derivative that acts as the inducer for the lacoperon.allopatric speciation Process of speciation associated with geographic isolation.Allopolyploid Polyploid condition formed by the union of two or more distinct chromosome sets with a subsequent doubling of chromosome number.allosteric effect Conformational change in the active site of a protein brought about by interaction with an effector molecule.Allotetraploid An allopolyploid containing two genomes derived from different species.allozyme An allelic form of a protein that can be distinguished from other forms by electrophoresis.alternative splicing Generation of different protein molecules from the same pre-mRNA by incorporation of a different set and order of exons into the mRNA product.Alusequence A DNA sequence of approximately 300 bp found interspersed within the genomes of primates that is cleaved by the restriction enzyme AluI. In humans, 300,000600,000 copies are dispersed throughout the genome and constitute some 36 percent of the genome. See short interspersed elements.amber codon The codon UAG, which does not code for an amino acid but for chain termination. One of the stop codons.Ames test A bacterial assay developed by Bruce Ames to detect mutagenic compounds; it assesses reversion to histidine independence in the bacterium Salmonella typhimurium.amino acids Aminocarboxylic acids comprising the subunits that are covalently linked to form proteins.aminoacyl tRNA A covalently linked combination of an amino acid and a tRNA molecule. Also referred to as a charged tRNA.amniocentesis A procedure in which fluid and fetal cells are withdrawn from the amniotic layer surrounding the fetus; used for genetic testing of the fetus.Amphidiploid Same as allotetraploid.Anabolism The metabolic synthesis of complex molecules from less complex precursors.Analog A chemical compound that differs structurally from a similar compound but whose chemical behavior is the same. Used experimentally to provide improved detection during analysis. See also base analog.anaphase Stage of mitosis or meiosis in which chromosomes begin moving to opposite poles of the cell.anaphase I The stage in the first meiotic division during which members of homologous pairs of chromosomes separate from one another.aneuploidy A condition in which the chromosome number is not an exact multiple of the haploid set.annotation Analysis of genomic nucleotide sequence data to identify the protein-coding genes, the nonprotein-coding genes, and the regulatory sequences and function(s) of each gene.antibody Protein (immunoglobulin) produced in response to an antigenic stimulus with the capacity to bind specifically to an antigen.Anticipation See genetic anticipation.Anticodon In a tRNA molecule, the nucleotide triplet that binds to its complementary codon triplet in an mRNA molecule.Glossary G-1G-2 GLOSSARY antigen A molecule, often a cell-surface protein, that is capable of eliciting the formation of antibodies.antiparallel A term describing molecules in parallel alignment but running in opposite directions. Most commonly used to describe the opposite orientations of the two strands of a DNA molecule.antisense oligonucleotide A short, single-stranded DNA or RNA molecule complementary to a specific sequence.antisense RNA An RNA molecule (synthesized in vivoor in vitro) with a ribonucleotide sequence that is complementary to part of an mRNA molecule.Apoptosis A genetically controlled program of cell death, activated as part of normal development or as a result of cell damage.artificial selection See selection.ascospore A meiotic spore produced in certain fungi.ascus In fungi, the sac enclosing the four or eight ascospores.asexual reproduction Production of offspring in the absence of any sexual process.assortative mating Nonrandom mating between males and females of a species. Positive assortative mating selects mates with the same genotype; negative selects mates with opposite genotypes.ATP Adenosine triphosphate, a nucleotide that is the main energy source in cells.attached-X chromosome Two conjoined X chromosomes that share a single centromere and thus migrate together during cell division.attenuator A nucleotide sequence between the promoter and the structural gene of some bacterial operons that regulates the transit of RNA polymerase, reducing transcription of the related structural gene.autogamy A process of self-fertilization resulting in homozygosis.autoimmune disease The production of antibodies that results from an immune response to ones own molecules, cells, or tissues. Such a response results from the inability of the immune system to distinguish self from nonself. Diseases such as arthritis, scleroderma, systemic lupus erythematosus, and juvenile-onset diabetes are autoimmune diseases.autonomously replicating sequences (ARS)Origins of replication, about 100 nucleotides in length, found in yeast chromosomes. ARS elements are also present in organelle DNA.autopolyploidy Polyploid condition resulting from the duplication of one diploid set of chromosomes.Autoradiography Production of a photographic image by radioactive decay. Used to localize radioactively labeled compounds within cells and tissues or to identify radioactive probes in various blotting techniques. See Southern blotting.autosomes Chromosomes other than the sex chromosomes. In humans, there are 22 pairs of autosomes.autotetraploid An autopolyploid condition composed of four copies of the same genome.auxotroph A mutant microorganism or cell line that requires a nutritional substance for growth that can be synthesized and is not required by the wild-type strain.backcross A cross between an F1heterozygote and one of the P1parents (or an organism with a genotype identical to one of the parents).bacteriophage A virus that infects bacteria, using it as the host for reproduction (also, phage).balanced lethals Recessive, nonallelic lethal genes, each carried on different homologous chromosomes. When organisms carrying balanced lethal genes are interbred, only organisms with genotypes identical to the parents (heterozygotes) survive.balanced polymorphism Genetic polymorphism maintained in a population by natural selection.balanced translocation carrier An individual with a chromosomal translocation in which there has been an exchange of genetic information with no associated extra or missing genetic material.balancer chromosome A chromosome containing one or more inversions that suppress crossing over with its homolog and which carries a dominant marker that is usually lethal when homozygous.Barr body Densely staining DNA-positive mass seen in the somatic nuclei of mammalian females. Discovered by Murray Barr, this body represents an inactivated X chromosome.base analog A purine or pyrimidine base that differs structurally from one normally used in biological systems but whose chemical behavior is the same. Used experimentally to provide improved detection during analysis, for example, 5-bromouracil, which “looks like” thymidine, substitutes for it, and can be detected because of its increased mass. See also analog.base pair See nucleotide pair.base substitution A single base change in a DNA molecule that produces a mutation. There are two types of substitutions: transitions, in which a purine is substituted for a purine, or a pyrimidine for a pyrimidine; and transversions, in which a purine is substituted for a pyrimidine or vice versa.B-DNA The conformation of DNA which is most often found in cells and serves as the basis of the Watson-Crick doublehelical model. There are 10 base pairs per full turn of its righthanded helix, with the nucleotides stacked 0.34 nm apart. The helix has a diameter of 2.0 nm.-galactosidase A bacterial enzyme, encoded by the lacZgene, that converts lactose into galactose and glucose.bidirectional replication A mechanism of DNA replication in which two replication forks move in opposite directions from a common origin.biodiversity The genetic diversity present in populations and species of plants and animals.bioinformatics A field that focuses on the design and use of software and computational methods for the storage, analysis, and management of biological information such as nucleotide or amino acid sequences.biometry The application of statistics and statistical methods to biological problems.Biotechnology Commercial and/or industrial processes that utilize biological organisms or products.Bivalents Synapsed homologous chromosomes in the first prophase of meiosis.BLAST (Basic Local Alignment Search Tool)Any of a family of search engines designed to compare or query nucleotide or amino acid sequences against sequences in databases. BLAST also calculates the statistical significance of the matches.Bombay phenotype A rare variant of the ABO antigen system in which affected individuals do not have A or B antigens and thus appear to have blood type O, even though their genotype may carry unexpressed alleles for the A and/or B antigens.Bottleneck See population bottleneck.bovine spongiform encephalopathy (BSE)A fatal, degenerative brain disease of cattle(transmissible to humans and other animals) caused by prion infection. Also known as mad cow disease.GLOSSARY G-3BrdU (5-bromodeoxyuridine)A mutagenically active analog of thymidine in which the methyl group at the 5position in thymine is replaced by bromine; also abbreviated BUdR.broad heritability That proportion of total phenotypic variance in a population that can be attributed to genotypic variance.buoyant density A property of particles (and molecules) that depends on their actual density, as determined by partial specific volume and degree of hydration.It provides the basis for density-gradient separation of molecules or particles.CAAT box A highly conserved DNA sequence found in the untranslated promoter region of eukaryotic genes. This sequence is recognized by transcription factors.cancer stem cells Tumor-forming cells in a cancer that can give rise to all the cell types in a particular form of cancer. These cells have the properties of normal stem cells: self-renewal and ability to differentiate into multiple cell types.CAP Catabolite activator protein; a protein that binds cAMP and regulates the activation of inducible operons.capillary electrophoresisA group of analytical methods that separates large and small charged molecules in a capillary tube by their size to charge ratio. Analysis of separated components takes place in the capillary usually by use of a UV detector.carcinogen A physical or chemical agent that causes cancer.carrier An individual heterozygous for a recessive trait.catabolism A metabolic reaction in which complex molecules are broken down into simpler forms, often accompanied by the release of energy.catabolite activator protein See CAP.catabolite repression The selective inactivation of an operon by a metabolic product of the enzymes encoded by the operon.cdcmutationA class of cell division cycle (cdc) mutations in yeasts that affect the timing of and progression through the cell cycle.cDNA (complementary DNA)DNA synthesized from an RNA template by the enzyme reverse transcriptase.cDNA library A collection of cloned cDNA sequences.cell cycle The sequence of growth phases of an individual cell; divided into G1 (gap 1), S (DNA synthesis), G2 (gap 2), and M (mitosis). A cell may temporarily or permanently be withdrawn from the cell cycle, in which case it is said to enter the G0 stage.cell-free extract A preparation of the soluble fraction of cells, made by lysing cells and removing the particulate matter, such as nuclei, membranes, and organelles. Often used to carry out the synthesis of proteins by the addition of specific, exogenous mRNA molecules.CEN The DNA region of centromeres critical to their function. In yeasts, fragments of chromosomal DNA, about 120 bp in length, that when inserted into plasmids confer the ability to segregate during mitosis.centimorgan (cM) A unit of distance between genes on chromosomes representing 1 percent crossing over between two genes. Equivalent to 1 map unit (mu).central dogma The concept that genetic information flow progresses from DNA to RNA to proteins. Although exceptions are known, this idea is central to an understanding of gene function.centric fusion See Robertsonian translocation.centriole A cytoplasmic organelle composed of nine groups of microtubules, generally arranged in triplets. Centrioles function in the generation of cilia and flagella and serve as foci for the spindles in cell division.Centromere The specialized heterochromatic chromosomal region at which sister chromatids remain attached after replication, and the site to which spindle fibers attach to the chromosome during cell division. Location of the centromere determines the shape of the chromosome during the anaphase portion of cell division. Also known as the primary constriction.Centrosome Region of the cytoplasm containing a pair of centrioles.CFTR The protein (cystic fibrosis transmembrane conductance regulator) encoded by the CFTR gene. The protein regulates the movement of chloride ions across the plasma membrane of epithelial cells. Mutations in CFTRlead to cystic fibrosis.chaperone A protein that regulates the folding of a polypeptide into a functional three-dimensional shape.character An observable phenotypic attribute of an organism.charon phages A group of genetically modified lambda phages designed to be used as vectors (carriers) for cloning foreign DNA. Named after the ferryman in Greek mythology who carried the souls of the dead across the River Styx.chemotaxis Movement of a cell or organism in response to a chemical gradient.chiasma (pl., chiasmata)The crossed strands of nonsister chromatids seen in diplotene of the first meiotic division. Regarded as the cytological evidence for exchange of chromosomal material, or crossing over.ChIP-on-chip A technique that combines chromatin immunoprecipitation (ChIP) with microarrays (chips) to identify and localize DNA sites that bind DNA-binding proteins of interest. These sites may be enhancers, promoters, transcription initiation sites, or other functional DNA regions.chi-square(X2) analysis Statistical test to determine whether or not an observed set of data is equivalent to a theoretical expectation.Chloroplast A self-replicating cytoplasmic organelle containing chlorophyll. The site of photosynthesis.chorionic villus sampling (CVS) A technique of prenatal diagnosis in which chorionic fetal cells are retrieved intravaginally and used to detect cytogenetic and biochemical defects in the embryo.Chromatid One of the longitudinal subunits of a replicated chromosome.chromatin The complex of DNA, RNA, histones, and nonhistone proteins that make up uncoiled chromosomes, characteristic of the eukaryotic interphase nucleus.chromatin immunoprecipitation (ChIP)An analytical method used to identify DNA-binding proteins that bind to DNA sequences