Balbiani ring A large chromosome puff. The larger polvtene chromosomal puffs. See chromosome puff Barr bod a densely staining mass that represents an inactivated X chromosome. Heterochromatic body found in the nuclei of normal females but absent in the nuclei of normal males basal body A short cylindrical array of microtubules and other proteins, found at the base of a eukaryotic cilium or flagellum, that organises the assembly of the axoneme(the bundle of microtubules and other proteins forming the core of each cilium or flagellum) base analogue a chemical whose molecular structure m mics that of a dna base because of the mimicry, the analogue may act as a mutagen Batesian mimicry Form of mimicry in which an innocuous mimic species gains protection by resembling noxious or dangerous model species bead theory The disproved hypothesis that genes are arranged on the chromosome like beads on a necklace. indivisible into smaller units of mutation and recombination beta-galactosidase The enzyme that splits lactose into glucose and galactose( coded by a gene(lac z) in the lac operon of Escher ichia col 1) beta-galactoside acetyltransferase An enzyme that is involved in lactose metabolism and encoded by a gene(lac a) in the lac operon of Escher ichi a coli) beta-galactoside permease An enzyme involved in concentrating lactose in the cell (coded by a gene(lac y) in the bimodal distribution a statistical distribution having two modes binary fission The process in which a parent cell splits into two daughter cells of approximately equal size. Simple cell division in single-celled organisms binomial expansion
Balbiani ring A large chromosome puff. The larger polytene chromosomal puffs. See chromosome puff. Barr body A densely staining mass that represents an inactivated X chromosome. Heterochromatic body found in the nuclei of normal females but absent in the nuclei of normal males. basal body A short cylindrical array of microtubules and other proteins, found at the base of a eukaryotic cilium or flagellum, that organises the assembly of the axoneme (the bundle of microtubules and other proteins forming the core of each cilium or flagellum). base analogue A chemical whose molecular structure mimics that of a DNA base; because of the mimicry, the analogue may act as a mutagen. Batesian mimicry Form of mimicry in which an innocuous mimic species gains protection by resembling noxious or dangerous model species. bead theory The disproved hypothesis that genes are arranged on the chromosome like beads on a necklace, indivisible into smaller units of mutation and recombination. beta-galactosidase The enzyme that splits lactose into glucose and galactose (coded by a gene (lac z) in the lac operon of Escherichia coli). beta-galactoside acetyltransferase An enzyme that is involved in lactose metabolism and encoded by a gene (lac a) in the lac operon of Escherichia coli). beta-galactoside permease An enzyme involved in concentrating lactose in the cell (coded by a gene (lac y) in the lac operon of Escherichia coli)). bimodal distribution A statistical distribution having two modes. binary fission The process in which a parent cell splits into two daughter cells of approximately equal size. Simple cell division in single-celled organisms. binomial expansion
The terms generated when a binomial expression [eg(p+q] is raised to a particular ower n [eg (p+qn binomial theorem The theorem that gives the terms of the expansion of a binomial expression [eg(p+q) sed to a biochemical genetics The study of the relationships between genes and enzymes, specifically the role of genes in controlling the steps in biochemical pathways biolistic A method(biological ballistics) of transfecting cells by bombarding them with microprojectiles coated with DNA biological species concept Organisms are classified in the same species if they are potentially capable of nterbreeding and producing fertile offspring biparental zygote A Chlamydomonas zygote that contains chloroplast DNA (cpDNA) from both parents, such cells generally are rare since normally cpDNA is inherited uniparentally from the mt+ mating type parent. These rare biparental zygotes allowed mapping of chloroplast bivalent Structure, formed during prophase of meiosis 1, consisting of synapsed homologous chromosomes. Equivalent to a tetrad of chromatids blastoderm In an insect embryo, the layer of cells that completely surrounds an internal mass of yolk blastomere One of the cells formed by division of the fertilized egg making up the blastula. blastopore The embryonic structure present during gastrulation and formed by invagination of the endoderm blastula An early developmental stage of vertebrate embryos formed by cleavage of the fertilized egg, in which the embryo consists of a single layer of cells surrounding a cavity(the blastocoel) blending inheritance
The terms generated when a binomial expression [eg. (p+q)] is raised to a particular power n [eg. (p+q)^n]. binomial theorem The theorem that gives the terms of the expansion of a binomial expression [eg. (p+q)] raised to a particular power n [eg. (p+q)^n]. biochemical genetics The study of the relationships between genes and enzymes, specifically the role of genes in controlling the steps in biochemical pathways. biolistic A method (biological ballistics) of transfecting cells by bombarding them with microprojectiles coated with DNA. biological species concept Organisms are classified in the same species if they are potentially capable of interbreeding and producing fertile offspring. biparental zygote A Chlamydomonas zygote that contains chloroplast DNA (cpDNA) from both parents, such cells generally are rare since normally cpDNA is inherited uniparentally from the mt+ mating type parent. These rare biparental zygotes allowed mapping of chloroplast genes by recombination. bivalent Structure, formed during prophase of meiosis 1, consisting of synapsed homologous chromosomes. Equivalent to a tetrad of chromatids. blastoderm In an insect embryo, the layer of cells that completely surrounds an internal mass of yolk. blastomere One of the cells formed by division of the fertilized egg making up the blastula. blastopore The embryonic structure present during gastrulation and formed by invagination of the endoderm. blastula An early developmental stage of vertebrate embryos formed by cleavage of the fertilized egg, in which the embryo consists of a single layer of cells surrounding a cavity (the blastocoel). blending inheritance
A discredited model of inheritance suggesting that the characteristics of an individual result from the smooth blending of fluid like influences from its parents blunt-end ligation The ligating or attaching of blunt-ended pieces of dna by T4 DNA ligase. Used in creating hybrid vectors bottleneck a brief reduction in size of a population which usually leads to random genetic drift brachydactyly A human phenotype of unusually short digits, generally inherited as an autosomal dominant branch migration 1. The process in which a crossover point between two DNA duplexes slides along the duplexes 2. The process by which a single invading DNA strand extends its partial pairing with its complementary strand as it displaces the resident strand from a DNA duplex breakage and reunion The general mode by which recombination occurs. DNA duplexes are broken and reunited in a crosswise fashion according to the Holliday model breakage-fusion-bridge cycle Damage that happens to a dicentric chromosome during each cell cycle bridging cross A cross made to transfer alleles between two sexually isolated species by first transferring the alleles to an intermediate species that is sexually compatible with both broad heritability(H 2) The proportion of total phenotypic variance at the population level that is contributed by bud a daughter cell formed by mitosis in yeast; one daughter cell retains the cell wall of the parent, and the other(the bud) forms a new cell wall buoyant density A measure of the tendency of a substance to float in some other substance, large nolecules are distinguished by their differing buoyant densities in some standard fluid Measured by density-gradient ultracentrifugation buoyant density of DNa
A discredited model of inheritance suggesting that the characteristics of an individual result from the smooth blending of fluid like influences from its parents. blunt-end ligation The ligating or attaching of blunt-ended pieces of DNA by T4 DNA ligase. Used in creating hybrid vectors. bottleneck A brief reduction in size of a population which usually leads to random genetic drift. brachydactyly A human phenotype of unusually short digits, generally inherited as an autosomal dominant. branch migration 1. The process in which a crossover point between two DNA duplexes slides along the duplexes. 2. The process by which a single invading DNA strand extends its partial pairing with its complementary strand as it displaces the resident strand from a DNA duplex. breakage and reunion The general mode by which recombination occurs. DNA duplexes are broken and reunited in a crosswise fashion according to the Holliday model. breakage-fusion-bridge cycle Damage that happens to a dicentric chromosome during each cell cycle. bridging cross A cross made to transfer alleles between two sexually isolated species by first transferring the alleles to an intermediate species that is sexually compatible with both. broad heritability (H^2) The proportion of total phenotypic variance at the population level that is contributed by genetic variance. bud A daughter cell formed by mitosis in yeast; one daughter cell retains the cell wall of the parent, and the other (the bud) forms a new cell wall. buoyant density A measure of the tendency of a substance to float in some other substance; large molecules are distinguished by their differing buoyant densities in some standard fluid. Measured by density-gradient ultracentrifugation. buoyant density of DNA
A measure of the density of dna determined by the equilibrium point reached by dnA Burkitt lymphoma A cancer of the lymphatic system manifested by tumours in the jaw, often associated with a translocation bringing a specific oncogene next to a novel regulatory element 夏 Back to Bto home page Jump to Terms beginning with D|旦 P LMN0 T E Ca-Cn F z Co-Cz G K 2μ(2 micron) plasmid A naturally occurring extragenomic (not part of the genome) circular DNA molecule found in some yeast cells, with a circumference of 2u. Engineered to form the basis for several types of gene vectors in yeast. Adenine or adenosine A(aminoacyl) site The site on the ribosome occupied by an aminoacyl-trna just prior to peptide bond a form dna The form of DNA at high humidity; it has tilted base pairs and more base pairs per turn than does b dna abortive transduction The failure of a transducing DNA segment to be incorporated into the recipient acentric chromosome acentric fragment a chromosomal piece without a centromere achondroplasia A type of dwarfism in humans inherited as an autosomal dominant phenotype
A measure of the density of DNA determined by the equilibrium point reached by DNA after density gradient centrifugation. Burkitt lymphoma A cancer of the lymphatic system manifested by tumours in the jaw, often associated with a translocation bringing a specific oncogene next to a novel regulatory element. ¤ B a ck t o B TO h ome p age Jump to Terms beginning with: A B Ca-Cn Co-Cz D E F G H I J K L M N O P Q R S T U V W X Y Z 2µ (2 micron) plasmid A naturally occurring extragenomic (not part of the genome) circular DNA molecule found in some yeast cells, with a circumference of 2µ. Engineered to form the basis for several types of gene vectors in yeast. A Adenine or adenosine. A (aminoacyl) site The site on the ribosome occupied by an aminoacyl-tRNA just prior to peptide bond formation. A form DNA The form of DNA at high humidity; it has tilted base pairs and more base pairs per turn than does B DNA. abortive transduction The failure of a transducing DNA segment to be incorporated into the recipient chromosome. acentric chromosome A chromosome having no centromere. acentric fragment A chromosomal piece without a centromere. achondroplasia A type of dwarfism in humans inherited as an autosomal dominant phenotype
acrocentric chromosome a chromosome whose centromere lies very near one end. See also metacentric chromosome activation energy (delta) Energy needed to initiate a chemical reaction active site The part of a protein that must be maintained in a specific shape if the protein is to be functional, for example, the part to which the substrate binds in an enzyme. The part of an enzyme where the actual enzymatic function is performed adaptation In the evolutionary sense, some heritable feature of an individuals phenotype that improves its chances of survival and reproduction in the existing en adaptive landscape The surface plotted in a three-dimensional graph; with all possible combinations of allele frequencies for different loci plotted in the plane; and mean fitness for each combination plotted in the third dimension daptive peak a high point(perhaps one of several)on an adaptive landscape, selection tends to drive the genotype composition of the population toward a combination corresponding to an adaptive surface adaptive value See fitness additive genetic variance Genetic variance associated with the average effects of substituting one allele for another additive model A mechanism of quantitative inheritance in which alleles at different loci either add a fixed amount to the phenotype or add nothing adenine A purine base that pairs with thymine in the dNA double helix. See purines adenosine
acrocentric chromosome A chromosome whose centromere lies very near one end. See also metacentric chromosome activation energy (deltaG) Energy needed to initiate a chemical reaction. active site The part of a protein that must be maintained in a specific shape if the protein is to be functional, for example, the part to which the substrate binds in an enzyme. The part of an enzyme where the actual enzymatic function is performed. adaptation In the evolutionary sense, some heritable feature of an individual's phenotype that improves its chances of survival and reproduction in the existing environment. adaptive landscape The surface plotted in a three-dimensional graph; with all possible combinations of allele frequencies for different loci plotted in the plane; and mean fitness for each combination plotted in the third dimension. adaptive peak A high point (perhaps one of several) on an adaptive landscape; selection tends to drive the genotype composition of the population toward a combination corresponding to an adaptive peak. adaptive surface See adaptive landscape. adaptive value See fitness. additive genetic variance Genetic variance associated with the average effects of substituting one allele for another. additive model A mechanism of quantitative inheritance in which alleles at different loci either add a fixed amount to the phenotype or add nothing. adenine A purine base that pairs with thymine in the DNA double helix. See purines. adenosine