A protein that when bound at its normal attachment sites in DNA, lets RNA polymerase read through nomal terminator sequences (eg the N-and Q-gene products of phage AP endonuclease endonuclease that initiates excision repair at apurinic and apyrimidinic sites on dNA AP site Apurinic or apyrimidinic site resulting from the loss of a purine or pyrimidine residue from the dna g Arginine(an amino acid) ascospore A sexual spore from certain fungus species in which spores are found in a sac called an ascus. Haploid spores found in the asci of Ascomycete fungi ascus In fungi, a sac that encloses a tetrad or an octad of ascospores. The sac in Ascomycete fungi that holds the ascospores asexual spore Asparagine(an amino acid) sp spartate(an amino acid assignment test a test that determines whether a locus is on a specific human chromosome by observation of the concordance of the locus and the specific chromosome in a panel of human-mouse hybrid cell lines containing only one or a few of the normal set (22 autosomes, X and Y) of human chromosomes assortative mating The mating of individuals with similar phenotype ataxia-telangiectasia A disease(loss of muscle control, and reddening of the skin) in human beings caused by defect in DNA repair mechanisms induced by ionising radiation(X-rays, beta and alpha particles, gamma rays)
A protein that, when bound at its normal attachment sites in DNA, lets RNA polymerase read through normal terminator sequences (eg the N- and Q-gene products of phage lambda). AP endonuclease endonuclease that initiates excision repair at apurinic and apyrimidinic sites on DNA. AP site Apurinic or apyrimidinic site resulting from the loss of a purine or pyrimidine residue from the DNA. Arg Arginine (an amino acid). ascospore A sexual spore from certain fungus species in which spores are found in a sac called an ascus. Haploid spores found in the asci of Ascomycete fungi. ascus In fungi, a sac that encloses a tetrad or an octad of ascospores. The sac in Ascomycete fungi that holds the ascospores. asexual spore See spore. Asn Asparagine (an amino acid). Asp Aspartate (an amino acid). assignment test A test that determines whether a locus is on a specific human chromosome by observation of the concordance of the locus and the specific chromosome in a panel of human-mouse hybrid cell lines containing only one or a few of the normal set (22 autosomes, X and Y) of human chromosomes. assortative mating The mating of individuals with similar phenotypes. ataxia-telangiectasia A disease (loss of muscle control, and reddening of the skin) in human beings caused by a defect in DNA repair mechanisms induced by ionising radiation (X-rays, beta and alpha particles, gamma rays)
ATP triphosphate) The energy molecule of cells, synthesized mainly in mitochondria and chloroplasts; energy from the breakdown of ATP drives many important reactions in the cell attached A pair of Drosophila X chromosomes joined at one end and inherited as a single unit attenuator A control region at the promoter end of repressible amino acid operons that exerts transcriptional control based on the translation of a small leader peptide gene. A region adjacent to the structural genes of the trp(tryptophan) operon; in the presence of tryptophan this region acts to reduce the rate of transcription from the structural genes attenuator stem A configuration of the leader transcript that signals transcription termination attenuator-controlled amino acid operons autogamy nuclear reorganization in a single Paramecium cell similar to the changes that occur during conjugation autonomous replication sequence(ars) A segment of a DNA molecule necessary for the initiation of its replication; generally a site recognized and bound by the proteins of the replication system autopolyploid a polyploid formed from the doubling of a single genome. Polyploidy in which all the chromosomes come from the same species autoradiography a process by which radioactive materials, often though not exclusively incorporated into cell structures, are located by exposure to a photographic emulsion forming a pattern on the film corresponding to the location of the radioactive compounds within the cell. A technique in which radioactive molecules make their location known by exposing photographic films or emulsions autoregulation The control of the transcription of a gene by its own gene product autosomal set The non-sex chromosomes consisting of one from each homologous pair in a diploid
ATP (adenosine triphosphate) The energy molecule of cells, synthesized mainly in mitochondria and chloroplasts; energy from the breakdown of ATP drives many important reactions in the cell. attached X A pair of Drosophila X chromosomes joined at one end and inherited as a single unit. attenuator A control region at the promoter end of repressible amino acid operons that exerts transcriptional control based on the translation of a small leader peptide gene. A region adjacent to the structural genes of the trp (tryptophan) operon; in the presence of tryptophan this region acts to reduce the rate of transcription from the structural genes. attenuator stem A configuration of the leader transcript that signals transcription termination in attenuator-controlled amino acid operons. autogamy nuclear reorganization in a single Paramecium cell similar to the changes that occur during conjugation. autonomous replication sequence (ARS) A segment of a DNA molecule necessary for the initiation of its replication; generally a site recognized and bound by the proteins of the replication system. autopolyploid A polyploid formed from the doubling of a single genome. Polyploidy in which all the chromosomes come from the same species. autoradiography A process by which radioactive materials, often though not exclusively incorporated into cell structures, are located by exposure to a photographic emulsion forming a pattern on the film corresponding to the location of the radioactive compounds within the cell. A technique in which radioactive molecules make their location known by exposing photographic films or emulsions. autoregulation The control of the transcription of a gene by its own gene product. autosomal set The non-sex chromosomes consisting of one from each homologous pair in a diploid species
autosome Any chromosome that is not a sex chromosome autotroph Organism that is able to utilize carbon dioxide as a carbon source autozygosity homozygosity in which the two alleles are identical by descent (ie they are copies of an auxotroph An organism with specific nutritional requirements auxotrophic mutant A mutant strain of microorganism that will proliferate only when the medium is supplemented with some specific substance not required by wild-type organisms axoneme a bundle of microtubules and other proteins forming the core of each cilium or flagellum B form dnA A right-handed double-helical conformation of DNA normally seen in solution described by Watson and Crick. A second DNA conformation(A form) is seen in unhydrated DNA ba acillus A rod-shaped bacterium back mutation The process that causes reversion. a change in a nucleotide pair in a mutant gene that restores the original sequence and hence the original phenotype backcross The cross of an individual with one of its parents or an organism with the same genotype as a parent. bacterial lawn A continuous cover of bacteria on the surface of a growth medium bacteriophage(phage balanced lethal system
autosome Any chromosome that is not a sex chromosome. autotroph Organism that is able to utilize carbon dioxide as a carbon source. autozygosity homozygosity in which the two alleles are identical by descent (ie they are copies of an ancestral gene) . auxotroph An organism with specific nutritional requirements. auxotrophic mutant A mutant strain of microorganism that will proliferate only when the medium is supplemented with some specific substance not required by wild-type organisms. axoneme A bundle of microtubules and other proteins forming the core of each cilium or flagellum. B form DNA A right-handed double-helical conformation of DNA normally seen in solution described by Watson and Crick. A second DNA conformation (A form) is seen in unhydrated DNA (fibres or crystals of oligonucleotides). bacillus A rod-shaped bacterium. back mutation The process that causes reversion. A change in a nucleotide pair in a mutant gene that restores the original sequence and hence the original phenotype. backcross The cross of an individual with one of its parents or an organism with the same genotype as a parent. bacterial lawn A continuous cover of bacteria on the surface of a growth medium. bacteriophage(phage) A virusthat infects bacteria. balanced lethal system
An arrangement of recessive lethal alleles that maintains a heterozygous chromosome combination homozygotes for any lethal-bearing chromosome perish balanced polymorphism Stable genetic polymorphism maintained by natural selection. Balbiani ring A large chromosome puff. The larger polytene chromosomal puffs. See chromosome puff B arr 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 theol 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 ichi a coli) beta-galactoside acetyltransferase An enzyme that is involved in lactose metabolism and encoded by a gene(lac a)in the lac operon of Escher ichia col i) 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
An arrangement of recessive lethal alleles that maintains a heterozygous chromosome combination. homozygotes for any lethal-bearing chromosome perish. balanced polymorphism Stable genetic polymorphism maintained by natural selection. 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 power n eg (p+qn binomial theorem The theorem that gives the terms of the expansion of a binomial expression [eg.(p+q) biochemical genetic raised to a particular power n leg(p+qn 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 ChI amydomonas 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 enes by recombination bivalent Structure, formed during prophase of meiosis 1, consisting of synapsed homologous chromosomes. Equivalent to a tetrad of chromatid 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
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 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