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 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 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 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 producing several different mRNAs and protein products altruism a form of behaviour in which an individual risks lowering its fitness for the benefit ofallopatric 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 producing several different mRNAs and protein products. altruism A form of behaviour in which an individual risks lowering its fitness for the benefit of