The nucleoside containing adenine as its base adenosine triphosphate See atp adjacent segregation In a reciprocal translocation heterozygote during meiosis the segregation of a translocated and a normal chromosome together, giving unbalanced gametes with duplications and deficiencies leading to non-viable zygotes. Adjacent segregation is of two kinds depending on whether non-homologous (adjacent-1)or homologous (adjacent-2) ion is the usual type of adjacent segregation, adjacent-2 segregation is rare adjacent-l segregation segregation of non-homologous centromeres during meiosis in a reciprocal translocation heterozygote such that unbalanced gametes with duplications and deficiencies are produced. See alternate segregation and adiacent-2 segregation adjacent-2 segregation tral such that unbalanced gametes with duplications and deficiencies are produced. See alternate segregation and adiacent-1 segregation ADP Adenosine diphosphate affected Individuals in a that exhibit the specific phenotype under study Ala Alanine(an amino acid) albino A pigmentless white phenotype, determined by a mutation in a gene coding for a pigment-synthesizing alkylating agent A chemical agent that can add alkyl groups(for example, ethyl or methyl groups)to another molecule, many mutagens act through alkylation alllele Alternative form of a gene. One of the different forms of a gene that can exist at a single allele frequenc
The nucleoside containing adenine as its base. adenosine triphosphate See ATP. adjacent segregation In a reciprocal translocation heterozygote during meiosis the segregation of a translocated and a normal chromosome together, giving unbalanced gametes with duplications and deficiencies leading to non-viable zygotes. Adjacent segregation is of two kinds depending on whether non-homologous (adjacent-1) or homologous (adjacent-2) centromeres segregate together. Adjacent-1 segregation is the usual type of adjacent segregation, adjacent-2 segregation is rare. adjacent-1 segregation segregation of non-homologous centromeres during meiosis in a reciprocal translocation heterozygote such that unbalanced gametes with duplications and deficiencies are produced. See alternate segregation and adjacent-2 segregation. adjacent-2 segregation segregation of homologous centromeres during meiosis in a translocation heterozygote such that unbalanced gametes with duplications and deficiencies are produced. See alternate segregation and adjacent-1 segregation. ADP Adenosine diphosphate. affected Individuals in a pedigree that exhibit the specific phenotype under study. Ala Alanine (an amino acid). albino A pigmentless white phenotype, determined by a mutation in a gene coding for a pigment-synthesizing enzyme. alkylating agent A chemical agent that can add alkyl groups (for example, ethyl or methyl groups) to another molecule; many mutagens act through alkylation. allele Alternative form of a gene. One of the different forms of a gene that can exist at a single locus. allele frequency
Often called gene frequency. A measure of how common an allele is in a population; the proportion of all alleles at one gene locus that are of one specific type in a population allelic exclusion a process whereby only one immunoglobulin light chain and one heavy chain gene are transcribed in any one cell, the other genes are repressed allopatric speciation speciation in which the evolution of reproductive isolating mechanisms occurs during physical separation of the populations allopolyploid polyploid produced by the hybridization of two species. See amphidiploid allosteric protein a protein whose shape is changed when it binds a particular molecule. In the new sha the protein,'s ability to react to a second molecule is altered allosteric transition a change from one conformation of a protein to another lloth The protein product (or the result of its activity )of an allele which may be detected as an antigen in another member of the same species (eg histocompatibility antigens, immunoglobulins), obeying the rules of simple Mendelian inheritance allozygosity homozygosity in which the two alleles are alike but unrelated See autozygosity allozyme Form of an enzvme that differs in amino acid sequence, as shown by electrophoretic mobility or some other property, from other forms of the same enzyme and is encoded by one allele at a single locus. See isozymes alternate segregation I translocation he normal chromosomes to one pole and both translocated chromosomes to the other pole, Segrega reciprocal translocation heterozygote such that genetically balanced gametes are alternation of generations The alternation of gametophyte and sporophyte stages in the life cycle of a plant alternative splicing
Often called gene frequency. A measure of how common an allele is in a population; the proportion of all alleles at one gene locus that are of one specific type in a population. allelic exclusion A process whereby only one immunoglobulin light chain and one heavy chain gene are transcribed in any one cell; the other genes are repressed. allopatric speciation speciation in which the evolution of reproductive isolating mechanisms occurs during physical separation of the populations. allopolyploid polyploid produced by the hybridization of two species. See amphidiploid. allosteric protein A protein whose shape is changed when it binds a particular molecule. In the new shape the protein's ability to react to a second molecule is altered. allosteric transition A change from one conformation of a protein to another. allotype The protein product (or the result of its activity) of an allele which may be detected as an antigen in another member of the same species.(eg histocompatibility antigens, immunoglobulins), obeying the rules of simple Mendelian inheritance. allozygosity homozygosity in which the two alleles are alike but unrelated. See autozygosity. allozyme Form of an enzyme that differs in amino acid sequence, as shown by electrophoretic mobility or some other property, from other forms of the same enzyme and is encoded by one allele at a single locus. See isozymes. alternate segregation At meiosis in a reciprocal translocation heterozygote, the passage (segregation) of both normal chromosomes to one pole and both translocated chromosomes to the other pole, giving genetically balanced gametes. Segregation of centromeres during meiosis in a reciprocal translocation heterozygote such that genetically balanced gametes are produced. alternation of generations The alternation of gametophyte and sporophyte stages in the life cycle of a plant. alternative splicing
Various ways of splicing out introns in eukaryotic pre-mRNAs resulting in one gene ducing several different mRNAs and protein prod altruism A form of behaviour in which an individual risks lowering its fitness for the benefit of another Alu family A dispersed intermediately repetitive DNA sequence found in the human genome in about three hundred thousand copies. The sequence is about 300 bp long. The name Alu comes from the restriction endonuclease alul that cleaves it amber codon The codon UAG. a nonsense codon amber suppressor A mutant allele coding for a tRNa whose anticodon is altered in such a way that the suppressor tRNA inserts an amino acid at an amber codon in translation suppressing (preventing)termination Ames test a widely used test to detect possible chemical carcinogens; based on mutagenicity in the acterium Salmonella amino acid The basic building block of proteins(or polypeptides). Containing a basic amino(NH2) group, an acidic carboxyl(COoH) group and a side chain(r-of a number of different kinds)attached to an alpha carbon atom. Thus NH2-C-CO0H aminoacyl-tRNA Transfer RNA (tRNA)molecule with its cognate amino acid attached aminoacyl-tRNA synthetase enzyme that attaches an amino acid to its cognate trNa(s amniocentesis A technique for testing the genotype of an embryo or fetus in utero with minimal risk to he mother or the child amorph
Various ways of splicing out introns in eukaryotic pre-mRNAs resulting in one gene producing several different mRNAs and protein products. altruism A form of behaviour in which an individual risks lowering its fitness for the benefit of another. Alu family A dispersed intermediately repetitive DNA sequence found in the human genome in about three hundred thousand copies. The sequence is about 300 bp long. The name Alu comes from the restriction endonuclease AluIthat cleaves it. amber codon The codon UAG, a nonsense codon. amber suppressor A mutant allele coding for a tRNA whose anticodon is altered in such a way that the suppressor tRNA inserts an amino acid at an amber codon in translation suppressing (preventing) termination. Ames test A widely used test to detect possible chemical carcinogens; based on mutagenicity in the bacterium Salmonella. amino acid The basic building block of proteins (or polypeptides). Containing a basic amino (NH2) group, an acidic carboxyl (COOH) group and a side chain (R - of a number of different kinds) attached to an alpha carbon atom. Thus: R | NH2-C-COOH | H aminoacyl-tRNA Transfer RNA (tRNA) molecule with its cognate amino acid attached. aminoacyl-tRNA synthetase enzyme that attaches an amino acid to its cognate tRNA(s). amniocentesis A technique for testing the genotype of an embryo or fetus in utero with minimal risk to the mother or the child. amorph
A mutant showing the complete lack of some normal substance or structure AMP Adenosine monophosphat amphidiploid An allopolyploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling. An organism produced by hybridization of two species followed by chromosome doubling. An allotetraploid that appears to be a normal diploid amplification of DNA The production of many DNA copies from one or a few copies anagenesis The evolutionary process whereby one species evolves into another without any splitting of the phylogenetic tree. See cladogenesis anaphase The stage of meiosis and mitosis in which sister chromatids(meiosisln) or homologous chromosomes(mitosis and meiosis) are separated by spindle fibers. An intermediate stage of nuclear division during which chromosomes or chromatids are pulled to the poles of the spindle aneuploid cell A cell having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes aneuploid Individuals or cells exhibiting aneuploidy aneu ploidy The condition of a cell or of an organism that has additions or deletions of a small number of whole chromosomes from the expected balanced diploid number of chromosomes angiosperm Plant whose seeds are enclosed within an ovary. Flowering plants animal breeding The practical application of genetic analysis for development of lines of domestic animals suited to human purposes annealing Spontaneous alignment of two complementary single polynucleotide(RNA, or DNA,or RNA and DNA)strands to form a double helix
A mutant showing the complete lack of some normal substance or structure. AMP Adenosine monophosphate. amphidiploid An allopolyploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling. An organism produced by hybridization of two species followed by chromosome doubling. An allotetraploid that appears to be a normal diploid. amplification of DNA The production of many DNA copies from one or a few copies. anagenesis The evolutionary process whereby one species evolves into another without any splitting of the phylogenetic tree. See cladogenesis. anaphase The stage of meiosis and mitosis in which sister chromatids (meiosisII) or homologous chromosomes (mitosis and meiosisI) are separated by spindle fibers. An intermediate stage of nuclear division during which chromosomes or chromatids are pulled to the poles of the spindle. aneuploid cell A cell having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes. aneuploid Individuals or cells exhibiting aneuploidy. aneuploidy The condition of a cell or of an organism that has additions or deletions of a small number of whole chromosomes from the expected balanced diploid number of chromosomes. angiosperm Plant whose seeds are enclosed within an ovary. Flowering plants. animal breeding The practical application of genetic analysis for development of lines of domestic animals suited to human purposes. annealing Spontaneous alignment of two complementary single polynucleotide (RNA, or DNA, or RNA and DNA) strands to form a double helix
anti-oncogene a gene that prevents malignant(cancerous)growth and whose absence, by mutation, results in malignancy(eg retinoblastoma) antibod a protein produced by a B lymphocyte that protects the organism against an antigen. A protein(immunoglobulin) molecule, produced by the immune system, that recognizes a particular foreign antigen and binds to it, if the antigen is on the surface of a cell, this binding leads to cell aggregation and subsequent destruction anticoding strand The DNa strand that forms the template for both the transcribed mRNA and the coding DNA strand anticodon The three-base sequence in tRNA complementary to a codon on mRNA. A nucleotide triplet in a tRNA molecule that aligns with a particular codon in mRNA under the influence of the ribosome, so that the amino acid carried by the tRNa is added to a growing protein chain antigen A molecule whose shape triggers the production of antibodies(immunoglobulins) that will bind to the antigen. a foreign substance capable of triggering an immune response in antimorph A mutant expressing some agent that antagonizes a normal gene product antimutator mutation mutation of dNa polymerase that decreases the overall mutation rate antiparallel A term used to describe the opposite orientations of the two strands of a dNa double helix; the 5 end of one strand aligns with the 3'end of the other strand antisense RNA RNA product of mic(mRNA-interfering complementary RNA) genes that regulates another gene by base pairing with and thus preventing translation from its mRNA antisense strand See ant antiterminator protein
anti-oncogene A gene that prevents malignant (cancerous) growth and whose absence, by mutation, results in malignancy (eg retinoblastoma). antibody A protein produced by a B lymphocyte that protects the organism against an antigen. A protein (immunoglobulin) molecule, produced by the immune system, that recognizes a particular foreign antigen and binds to it; if the antigen is on the surface of a cell, this binding leads to cell aggregation and subsequent destruction. anticoding strand The DNA strand that forms the template for both the transcribed mRNA and the coding DNA strand. anticodon The three-base sequence in tRNA complementary to a codon on mRNA. A nucleotide triplet in a tRNA molecule that aligns with a particular codon in mRNA under the influence of the ribosome, so that the amino acid carried by the tRNA is added to a growing protein chain. antigen A molecule whose shape triggers the production of antibodies (immunoglobulins) that will bind to the antigen. A foreign substance capable of triggering an immune response in an organism. antimorph A mutant expressing some agent that antagonizes a normal gene product. antimutator mutation mutation of DNA polymerase that decreases the overall mutation rate. antiparallel A term used to describe the opposite orientations of the two strands of a DNA double helix; the 5' end of one strand aligns with the 3' end of the other strand. antisense RNA RNA product of mic (mRNA-interfering complementary RNA) genes that regulates another gene by base pairing with and thus preventing translation from its mRNA. antisense strand See anticoding strand. antiterminator protein