In order to assess the relationship between genetic and environmental variability, a large natural population of Drosophila melanogaster was replicated as eight subpopulations, which were subjected to four different patterns of environmental variation. The environmental variable imposed was presence of 15% ethanol in the culture medium. Experimental treatments of the populations were intended to simulate constant environmental conditions, spatial heterogeneity in the environment, and two patterns of temporal environmental variation with different periodicity (long- and short-term temporal variation). Additive genetic and phenotypic variation in sternopleural and abdominal chaeta number, and body weight, were estimated in two successive years, and measurements were taken of the genotype–environment correlation of body weight and sternopleural bristle score with medium type.

Additive genetic variance of sternopleural chaeta number and of body weight was significantly greater in the three populations experiencing environmental heterogeneity than in the control population, but additive genetic variance of abdominal bristle score was not clearly affected by exposing populations to varying environments. Temporal environmental variation was equally, if not more, efficient in promoting the maintenance of genetic variation than spatial heterogeneity, but the cycle length of the temporal variation was of no consequence. Specific genotype–environment interactions were not present, therefore adaptation to heterogeneous environments is by selection of heterozygosity per se, rather than by differential survival of genotypes in the alternate niches.

A spontaneous autosomal mutation in C57BL/Tb mice, provisionally called reduced pigmentation, symbol rp, has pronounced effects on three kidney lysosomal glycosidase activities. Homozygous rprp mice have significantly higher activities of β-galactosidase, β-glucuronidase and N-acetyl-β-hexosaminidase than their heterozygous litter-mates. Homozygotes have light ears and tails, diluted fur and dark eyes. The mutation is not allelic to any known to affect lysosomal functions, or to a number of pigmentation variants with similar phenotypic effects. The locus is on chromosome 7.

The rudimentary locus of Drosophila melanogaster contains the structural information for the first three enzymes of the de novo pyrimidine pathway. Two new rudimentary (r) mutants have been isolated following mutagenesis with ICR-170. From complementation analysis and cyto-genetical observation both were shown to be deficiencies which expose the r locus. Df(1)r19 is deleted from band 14D1 to 15D1 and Df(1)r1D from band 14B6 to 15A2. These deficiencies were combined with several characterized r alleles each giving a single enzymatic defect in one of the first three enzymes of the pyrimidine pathway. An unusual semilethal trans effect was observed in some but not all the combinations. The effect was not observed with a third smaller deficiency which also exposes the rudimentary locus.

A mathematical theory of population genetics accounting for the genes transmitted through mitochondria or chloroplasts has been studied. In the model it is assumed that a population consists of Nm males and Nf females, the genetic contribution from a male is β and that from a female 1 – β, and each cell line contains n effective copies of a gene in its cytoplasm. Assuming selective neutrality and an infinite alleles model, it is shown that the sum (H) of squares of allelic frequencies within an individual and the corresponding sum (Q) for the entire population are, at equilibrium, given by

and

where ρ = 2β(1−β), Ne = {β2/Nm+(1−β)2 / Nf}−1, λ is the number of somatic cell divisions in one generation, and v is the mutation rate per cell division. If the genes are transmitted entirely through the female the formulae reduce to Ĥ ≃ 1/(1 + 2nv) and Q^ ≃ 1/{1 + (2Neλ+ 2n)υ}. Non-equilibrium behaviours of H and Q^ are also studied in the case of a panmictic population. These results are extended to geographically structured models, and applied to existing experimental data.

The major type I insert sequence for the 28S rRNA genes of Drosophila melanogaster has been mapped within the chromosomes using a probe synthesized from a cloned sequence containing the entire 5·4 kb segment. The genomic distribution was shown to be complex in that the insert sequence occurred next to many different types of sequences, in addition to occurring as an insert in the 28S rRNA genes of the X chromosome. In situ hybridization of mitotic chromosomes showed most of the insert units not contained in the ribosomal genes to be located near the ribosomal gene cluster on the X chromosome. Additional sites were detected in polytene chromosomes in region 102C, 8–12 and in the hetero-chromatin of the autosomes.

Michie's hypothesis of ‘affinity’ is invoked to explain how fertility might theoretically be achieved in a female mule or hinny. Chromosomally balanced haploid gametes could be produced in these inter-specific hybrids by movement of centromeres of similar ancestry to opposite poles at anaphase I of meiosis. Male hybrids could probably never be fertile on account of the low numbers of spermatozoa produced; females, on the other hand, might occasionally achieve fertility by the ovulation of a chromosomally balanced egg.

The genetically determined oocyte-specific expression of glucose-phosphate isomerase activity in the mouse is first apparent at 6 to 7 days after birth, and occurs in XO as well as in XX oocytes. The regulator locus that controls oocyte-specific expression shows the same linkage relations as the structural gene, suggesting that both form part of a Gpi-1 gene complex.

The broad host-range non-conjugative IncQ plasmid RSF1010 was mobilised with 100% efficiency in membrane filter matings, both in E. coli K12 and P. aeruginosa PAO, by broad host-range conjugative IncP plasmids. No homology between RSF1010 and an IncP plasmid could be detected. In E. coli, IncIα and IncX plasmids, but not IncF, IncN or IncW plasmids, were also relatively efficient at mobilising RSF1010, while in P. aeruginosa, R91–5 (IncP-10) was highly efficient, but pMG5 (IncP-2) and FP2 (IncP-8) were very inefficient. IncP plasmids also mobilised several plasmids derived from RSF1010 for use as in vectors in in vitro recombination experiments very efficiently, and pSC101 quite efficiently: this reduces the level of biological containment possible with these plasmids.

The title of the paper by Bailey et al. (Genetical Research 36, 167–180, 1980) should read:

‘A third gene affecting GABA transaminase levels in Aspergillus nidulans’

The possibility of using Hordeum bulbosum Crosses to facilitate production of disomic wheat–barley addition lines from monosomic additions was investigated. Aneuhaploids with 22 chromosomes were obtained in the expected gametic frequencies after crossing monosomic, disomio and monotelo-disomic addition lines, involving four different barley chromosomes, as the female parent with tetraploid H. bulbosum. Thus the added barley chromosomes were not eliminated when preferential elimination of the bulbosum chromosomes took place in the hybrid embryos. Disomic addition lines were obtained after treating the aneuhaploids with colchicine. This method could have wider application in the production of other wheat–alien chromosome disomic addition lines, especially where the transmission frequency of the alien chromosome through the pollen is very low, but its use will depend on the wheat parent being crossarle with H. bulbosum and the alien chromosome being retained during the elimination of bulbosum chromosomes.

The expression of X-linked phosphoglycerate kinase (PGK-1) in germ cells from embryos heterozygous for both PGK-1 and Searle's translocation T(X; 16) 16H was examined to investigate X chromosome activity during oogenesis. The Pgk-lb allele on the translocated X chromosome was the only allele active in somatic cells of all embryos and in germ cells from 12·5 d.p.c. embryos. However, an additional faint band representing Pgk-la activity was observed in germ cells from older embryos (13·5–18·5 d.p.c.) and neonates (1–2 d.p.p.). It is concluded that there is a period when only one X chromosome is active in early female germ cells and that reactivation of the inactive X chromosome takes place just prior to meiotic prophase.