This paper presents evidence that the alcohol dehydrogenases (ADHs) in barley are specified by three loci. Six distinct ADH isozymes are observed following native slab polyacrylamide gel electrophoresis of crude extracts from flooded wild-type roots. Three of these isozymes are missing in flooded roots of plants homozygous for the Adhl-M9 mutation. The results also indicate that a simple binomial model (incorporating random dimerization and no inhibitive interaction of the two subunit species within heterodimers) is unable to account for the distribution of the total ADH activity between the ADH isozymes observed. Finally, the level and distribution of ADH activity in heterozygous (Adhl+ / Adhl-M9) flooded roots is not what would be expected if these contain only one-half of the available ADH1 protomers and the same frequency of available ADH2 and ADH3 protomers as is contained in the flooded roots of wild-type homozygotes (Adhl + / Adhl + ).

Some 400 wild mice (Mus domesticus) from southern Germany (the triangle formed by the cities Tübingen, Heidenheim and Friedrichshafen) were karyotyped and, in 243 of them, the chromosome compositions were determined by banding techniques. Virtually all mice tested carried at least one pair of metacentric chromosomes; some mice had up to ten metacentric chromosomes. Based on their chromosome composition, five mouse populations could be distinguished. Population I was characterized by the diploid chromosome number of 2n = 38 and the presence of two copies of metacentric chromosome Rb(4.12)1Tu. This translocation was also found in virtually all mice captured in southern Germany, almost always in a homozygous state. Mice of other populations had extra metacentric chromosomes Rb(5.15)15Tu (population II), Rb(13.14)17Tu (population III), Rb(5.14)18Tu (population IV) and Rb(11.13)6Tu (population V). In addition, rare variants (1 or 2 mice) were found in the different populations, which were heterozygous for additional metacentric chromosomes. Population V was quite heterogeneous in that it contained up to five metacentric chromosomes in addition to those mentioned. The number and the composition of these metacentric chromosomes varied from place to place. With the exception of population I, the individual populations occupied geographically distinct areas: Representatives of population I were found concentrated in one area, but, in addition, some were scattered over the entire studied region.

A total of 207 wild mice trapped at different localities in southern Germany were tested for the presence of antigenic determinants controlled by class I genes (K and D) of the H-2 complex. The test was based on the complement-dependent killing of lymphocytes in the micro-cytotoxicity assay. Both private (allele-specific) and public (shared) determinants were tested using polyclonal and monoclonal antibodies. The results of the H-2 typing were in agreement with karyological typing which divided the sampled mice into 5 populations. Each population was characterized by a certain antigenic profile (occurrence of individual determinants at certain frequencies); the profiles of the individual populations were sufficiently unique to differentiate these populations but at the same time sufficiently similar to indicate common origin of the populations. The karyological typing of the same mice reveals that all 5 populations share 1 pair of metacentric chromosomes, Rb(4.12)1Tu, but that, in addition, each population has at least one metacentric chromosome differentiating it from other populations. We interpret these findings as evidence that all wild mice in southern Germany stem from a common stock in which the Rb(4.12)1Tu translocation became fixed and which subsequently differentiated into the individual populations. This differentiation is accompanied by the fixation of new Robertsonian translocations (different ones in different populations) and the acquisition of characteristic H-2 antigenic profiles.

We studied the amount of Mu(G+) and Mu(G−) phages in different Mu lysates prepared either upon induction or upon infection of E. coli and Erwinia strains. We also looked at the level of expression of the modification function (mom) by Mu(G−) phages, both after induction and after infection of E. coli and Erwinia. The expression of mom seems to be regulated in the same manner in E. coli and in the strain of Erwinia carotovora tested. The proportion of both types of Mu(G+) and Mu(G−) phages in induced lysates is very variable and we found growth conditions favouring the production of Mu(G−) particles. This should extend the use of Mu as a genetic tool and as a generalized transducing phage to many enterobacteria.

A mutant, YS17, at the buff spore colour locus in Sordaria brevicollis has previously been described. It shows conversion with high frequency, predominantly to wild type, and is believed to act as a recognition site for an endonuclease that initiates recombination at the YS17 site. The discovery is now reported of a gene that causes loss of the high-frequency conversion shown by the YS17 mutant. The gene was present in existing stocks of the fungus. It reduces the conversion frequency of YS17 to a level similar to that of other buff mutants, from which it is inferred that the YS17 mutant no longer acts as an initiation site for recombination. When the conversion frequency of YS17 is low the bias in conversion to wild type rather than to mutant is lost, suggesting that this bias may relate to the initiation of recombination at the site. The loss of high frequency conversion of YS17 appears to be determined by a single recessive gene linked to mating type and unlinked to buff. It is suggested that the dominant allele induces recombination at the site of YS17 by controlling either the synthesis or the activity of an endonuclease that is capable of recognising the nucleotide sequence at the YS17 site. Some anomalous results point to the existence of modifiers of the action of the gene.

Aneuploidy can result from a variety of defects at meiosis. Results are presented of crosses of Sordaria brevicollis in which aneuploid spores are detected through complementation of spore colour mutants at the buff or grey-6 loci on linkage groups II and IV respectively. By using ascus analysis, the underlying cause of the aneuploidy can be deduced in many cases. Thus non-conjuction (pairing failure) and non-disjunction at the first meiotic division, premature centromere division, non-disjunction at the second division, and pre-meiotic errors such as extra replication of the chromosomes can be distinguished. Both linkage groups were found to give a similar proportion of the different errors. Non-conjunction and first-division non-disjunction formed 60–70% of detectable cases, whilst premature centromere division and second-division non-disjunction comprised 10% and 5% of aneuploids respectively. However, only a small proportion of second-division errors are detected.

It is proposed that the systems described in this paper can form the basis of a valuable screening method for detecting agents which increase aneuploid frequency. The advantages and disadvantages of using lower eukaryotes in this way are discussed.

The zymogram phenotypes of 11 enzymes were determined for 22 Triticum aestivum cv. Chinese Spring-Elytrigia elongata disomic and ditelosomic chromosome addition lines. Eleven isozyme structural genes were located in specific arms of six E. elongata chromosomes, as follows: Gpi-E1 in 1ES, Est-E1 in 3ES, Got-E3 in 3EL, Adh-E1 and Lpx-E1 in 4ES, Adh-E2 and Lpx-E2 in 5EL, Amp-E1 in 6Eα, Adh-E3 and Got-E2 in 6Eβ, and Ep-E1 in 7EL. The E. elongata chromosomes present in five disomic addition lines have previously been designated 1E, 2E, 4E, 6E, and 7E to indicate their homoeology with Chinese Spring chromosomes. The results of this study support these designations. The development of disomic putative 3E and 5E addition lines is reported. The added chromosomes designated IV, V, and VI that are present in three of the seven original disomic T. aestivum-E. elongata addition lines are translocated. Evidence that VL and VIL are opposite arms of 2E and that IV is partially homoeologous to 3E has been published. The results reported in this paper indicate that IVS = 3ES, IVL = 7EL, VS = 3ES, and VIS = 5ES and are consistent with VL and VIL being opposite arms of 2E. The synteny relationships of the 11 E. elongata isozyme genes identified in this study are fully consistent with those of homoeologous T. aestivum cv. Chinese Spring genes and thus provide evidence that the gene synteny groups which these two species inherited from their common ancestor are conserved. This study further documents the valuable role that studies of isozyme genes can play in the isolation, characterization, and maintenance of alien chromosomes, telosomes, and chromosomal segments in wheat strains.

This report describes the existence of a mutation in a proA1 pabaA6 yA2 strain of Aspergillus nidulans, which prevents it growing on elevated concentrations of nitrite. The nitrite toxicity marker (nihA) resulted from a mutation in a single gene representing a new locus in linkage group I, and behaved as a recessive character. The observed recombination frequencies between nihA and proA1 and between nihA and pabaA6 were about 1 and 11%, respectively. Nitrite toxicity was not due to a defect in nitrite reductase, because the mutant grew well on nitrate. Furthermore, ammonium protected both nis-5 and niiA− strains against nitrite toxicity, which was not observed for the nihA strain. Since growth of the mutant was inhibited more by a mixture of ammonium and nitrite, compared to nitrite alone, it is proposed that the proA1 pabaA6 yA2 strain has a mutation leading to increased efficiency in nitrite uptake, which is not repressed by ammonium.

Structural genes for the isozymes of shikimate dehydrogenase (E.C. 1.1.1.25) have been located on chromosome arms 5AS, 5BS and 5DS of wheat, 5RS of cereal rye and on chromosome 5Cu of Aegilops umbellulata by electrophoretic techniques. This character provides a useful genetic marker for these previously unmarked chromosome arms, and the results support the notion of the conservation of gene synteny groups within the Triticinae.