A new CNR (caudatum non-reversal) mutant of Paramecium caudatum was isolated after gamma ray mutagenesis. This CNR lacks not only the transient inward Ca2+ current but also the sustained Ca2+ current. It was shown to complement the three known CNR mutants of P. caudatum (cnrA, cnrB and cnrC) by crossbreeding analyses. Thus, this new mutant belongs to a 4th CNR locus, designated cnrD. The defect of cnrD can be partially rescued by microinjection of cytoplasm from any of the three CNR mutants or the three Pawns (pwA, pwB and pwC) in P. tetraurelia. Since the three CNR genes have been shown to be different from the three Pawn genes by cytoplasmic complementation test (Haga et al. 1983), this result suggests that cnrD is the 7th non-excitable mutant in Paramecium. Thus, there are at least seven genes controlling Ca2+ channel function in Paramecium.

Genes controlling the synthesis of the D group of low-molecular-weight (LMW) subunits of glutenin occur on the short arms of chromosomes 1B and 1 D. Their position on chromosome 1 B, relative to the storage protein loci Glu-B1 (long arm) and Gli-B1 (short arm), was estimated by analysing the backcross-one progeny of two different crosses. To estimate recombination between the D subunit genes and Gli-B1, half grains were analysed by two-dimensional electrophoresis. The Gli-B1 locus contains genes for the B group of LMW glutenin subunits, γ-gliadins and ω-gliadins although only the latter were made use of in this study to distinguish the parental alleles. Additionally, the complementary half grains were analysed by sodium dodecyl sulphate, polyacrylamide-gel electrophoresis to estimate recombination between Gli-B1 and Glu B1, coding for high-molecular-weight (HMW) glutenin subunits. The D subunit genes occur at a new locus, provisionally defined as Glu-B2, which lies in between Glu-B1 and Gli-B1, 17 cM from the former and 22 cM from the latter. On the basis of previous mapping data involving Gli-B1, it was concluded that the D subunit genes occur close to the nucleolar organizing region and probably on the short-arm satellite, like Gli-B1.

Transcription in 9A–11A aneuploid mosaic female larvae of Drosophila melanogaster has been assessed autoradiographically. Eleven larvae were found to exhibit mosaicism out of sixty-six larvae scanned and the percentage of XO and XX nuclei varied from approximately 9 to 100. Irrespective of the number of XX nuclei present the XO nuclei (duplicated for 9A–11A) invariably showed hyperactivity for both the segments. The XX nucleus exhibited a dosage effect for all the three segments of 9A–11A. Results support the transcriptional constancy of the entire X chromosome, as proposed by Maroni and Lucchesi. Cellular autonomy of hyperactivity of the single X chromosome even at the level of segments of the X is thus evident from the present results.

By means of genetic mosaics we have studied the cell autonomy of mei-41 and mei-9, two loci involved in DNA metabolism. The frequency of spontaneous somatic spots resulting from unrepaired chromosome damage and the sensitivity of mutant cells to killing by X-irradiation - two traits indicative of deficient DNA repair - have been analysed at the cellular level. The results show that: (1) The effect of both mutations on chromosome stability is cell autonomous. (2) After 1000 r of X-irradiation practically all the cells homozygous for mei-41 disappear while about one-third of the cells homozygous for mei-9a survive the irradiation. The possibility of using these mutants as tools to approach developmental problems is discussed.

Examination of the eyes with a slit lamp revealed that 101/H mice had a coloured cataract. Crosses to C3H/HeH indicated that this was inherited as a single recessive gene which we have designated lop-2 (lens opacity-2). The related strain 129/Sv-SlJ-CP had a phenotypically identical cataract and presumably also carries the lop-2 gene. CBA/H, CBA/CaH- + /p, CBA/H-kd and CBA/H-T6 mice had a bright white or white/green cataract that typically extended from the nucleus to the anterior cortex of the lens. Crosses to C3H/HeH indicated that this was inherited as a semi-dominant gene. However, other crosses raise the possibility that the CBA cataract is also caused by lop-2. If so, the expressivity (and penetrance of the heterozygote) is affected by genetic background. Neither lop-2 nor the gene responsible for the CBA cataract was linked to contrasted (Slcon) on chromosome 10, so these are distinct from the Lop (lens opacity) gene. Further studies of genetic linkage are needed to clarify whether lop-2 is responsible for both the 101/H and CBA/H cataracts.

Weekly food intake and body weight were measured from 3 to 17 weeks of age on mice selected 14 generations for increased and decreased values of one of three criteria: appetite (A) as measured by 4- to 6-week food intake, adjusted by phenotypic regression to minimize change in 4-week body weight; fat percentage (F), using the ratio of gonadal fat pad weight to body weight at 10 weeks of age and total lean mass (protein, P), using the index body weight in 10-week males— (8 × gonadal fat pad weight). Carcass composition analyses were undertaken on the 17-week-old mice, and are presented along with composition data for younger mice from earlier generations. The high intake A line mice are larger, eat more, have higher maintenance requirements and are slightly leaner than the low intake A line mice, but are no more efficient. The increased lean mass P line mice are much larger, eat more and are more efficient than the decreased lean mass P line mice, but show little difference in maintenance or carcass composition. The (much) fatter F line mice are larger, more efficient and eat more during the rapid growth period than their leaner F line counterparts, but show no difference in lean mass or maintenance requirements. These results provide implications about the relationships between the input (intake) and output (maintenance and lean and fat deposition) components of growth.

The Haldane-Muller principle of mutation load is generalized so as to be applicable to both cases of strong and very weak selection with any time variation. It is proved that in an infinite asexual haploid population, the average Malthusian parameter m¯ of a population, the evolution rate ν, and the total mutation rate μ satisfy the relation ∂m¯/∂/∂μ = ν/μ−1, so long as each Malthusian parameter is independent of μ. A similar result is also true in a diploid population under genie selection. It is discussed how the above relation gives a restriction on the possible range of values of relative evolution rate ν/μ.

Aggregation chimaeras were made from embryos of C57BL/6 and BALB/c mice. Chimaeric and control females were mated with ICR males at 8 weeks of age and their litter sizes were evaluated over a 5-month period after the first mating. Progeny tests showed that 18 of 27 chimaeras produced oocytes of both genotypes. The mean litter sizes of C57BL/6, BALB/c and their F1 crosses (C57BL/6 × BALB/c and BALB/c × C57BL/6) were 8·14, 9·36, 13·38 and 13·40, respectively. The mean for chimaeras was 11·54 and chimaeric heterosis was evident, but it was not as much as heterosis in the F1 When the chimaeras were classified into the mixed and single-genotype progeny chimaeras, chimaeric heterosis was observed only in the mixed-progeny chimaeras. Quantitative GPI analyses in ten organs showed that the degree of chimaerism in the mixed-genotype progeny chimaeras was higher than that in most of the single-genotype progeny chimaeras and that the degree of chimaerism in the ovaries was positively correlated with litter size in the mixed-genotype progeny chimaeras. On the other hand, such correlation was not observed in the single-genotype progeny chimaeras.

The radiation-induced agouti allele a1 is recessive to the alleles a and a4H (which resembles ae). It is lethal when homozygous and also in combination with the dominant yellow allele Ay. The ethylnitrosourea induced allele a16H is also lethal when homozygous, and when heterozygous with a shows a phenotype like that of ax, with black back and lighter belly. Like ax it is not lethal with Ay, and it is also not lethal with a1, a1 is believed to be the first recessive allele which is lethal with Ay, and may be useful in elucidating the complexity of the agouti locus.

An experimental evaluation of Jódar & López-Fanjul's (1977) theoretical treatment of the optimum proportions to select when the numbers of males and females scored are unequal has been carried out for sternopleural bristle number in Drosophila melanogaster. Three different values of the sex-ratio (c) were considered (c = 1, 4 and 10) for the same total number of individuals scored per generation. For each c value two types of line were selected with proportions theoretically maximizing the response to be attained after 10 or 20 generations, respectively. Thus, there were six types of lines and each type was replicated sixfold. A good qualitative agreement was found between the observed and the expected rankings of the different types of selected lines at the designated generations.

DNA sequence comparison among homologous genes sampled at random from one or two populations allows one to estimate the ultimate amount of genetic variation maintained in a population and to construct the gene genealogy within and between populations. Moreover, if we use the finding of the molecular clock (Zuckerkandl & Pauling, 1965), it is also possible to estimate the divergence time of populations examined. Such an estimated divergence time is, however, intricately affected by samples and stochastic forces occurring in the course of evolution.