The mating system of a natural population of Bulinus globosus from the Chiweshe area, Zimbabwe, was studied with mother—offspring data using isozyme genetic markers. The study was done in response to work on the genetic structure of this population which suggested a limited extent of cross-fertilization. Of the 24 adults whose progenies were analysed, at least 15 showed evidence of outcrossing and 9 had results consistent with selfing. These results show that the two modes of reproduction are important under natural conditions and the mating system of this population is considered to be ‘partially-selfing’.

A close examination of reports on circling mutants of the mouse suggested that the commonly held view that the abnormalities of the inner ear are responsible for the waltzing syndrome was probably without foundation. It was thought that a study of kinky (Fuki/+) mice might resolve the doubt, because this mutant has the widest range of abnormalities of the inner ear and behaviour. The results showed that correlation between the two types of abnormalities, although high, was far from complete. This is interpreted as signifying that they are related collaterally rather than lineally. It is argued that they both originate in some primary abnormality of the central nervous system, and circumstantial evidence is presented in support of this argument. It is further suggested that the mode of gene action is essentially similar in all circling mutants, that is the abnormalities of the inner ear are consequent on some early abnormality of the neural tube and the ganglia in the region of the otic vesicle.

The details of the paper by Mittwoch et al. (Genetical Research44, 219–224, 1984) listed on the cover should read:

“Mittwoch, Ursula, Mahadevaiah, Shantha and Setterfield, Leslie. Chromosomal anomalies that cause male sterility in the mouse also reduce ovary size page 219”

The recessive tω5-haplotype, a complete haplotype, is transmitted by heterozygous male mice at very high frequencies (> 0·90) in normal matings. The present studies were undertaken to determine the effects of delayed matings and in vitro fertilizations on this phenotypic expression. Males carrying the tω5-haplotype ( + / tω5) were first tested for their frequencies of transmission of the mutant 17th chromosome in both normal and delayed matings. Spermatozoa obtained from these same males were then used to fertilize eggs in vitro. The in vivo and in vitro transmission frequencies were found to be statistically equivalent in all types of inseminations. An in vitro fertilization time course study showed that the same percentages of eggs are fertilized by tω5- bearing spermatozoa when the gametes are coincubated for either 2 or 6 h. The data lead to the conclusion that the transmission frequency of the tω5-haplotype is not affected either by the length of time elapsing between insemination and fertilization or by the environment in which fertilization occurs.

A didelphid marsupial, the gray short-tailed opossum (Monodelphis domestica), was used as a model species to study the biochemical genetics of alcohol dehydrogenases (ADHs) and aldehyde dehydrogenase (ALDH) in corneal tissue. Isoelectric point variants of corneal ALDH (designated ALDH3) and a major soluble protein in corneal extracts were observed among eight families of animals used in studying the genetics of these proteins. Both phenotypes exhibited identical patterns following PAGE-IEF and were inherited in a normal Mendelian fashion, with two alleles at a single locus (ALDH3) showing codominant expression. The data provided evidence for genetic identity of corneal ALDH with this major soluble protein, and supported biochemical evidence, recently reported for purified bovine corneal ALDH, that this enzyme constitutes a major portion of soluble corneal protein (Abedinia et al. 1990). Isoelectric point variants for corneal ADH were also observed, with patterns for the two major forms (ADH3 and ADH4) and one minor form (ADH5) being consistent with the presence of two ADH subunits (designated γ and δ), and variant phenotypes existing for the γ subunit. The genetics of this enzyme was studied in the eight families, and the results were consistent with codominant expression of two alleles at a single locus (designated ADH3). It is relevant that a major detoxification function has been proposed for corneal ADH and ALDH, in the oxidoreduction of peroxidic aldehydes induced by available oxygen and UV-B light (Holmes & VandeBerg, 1986a). In addition, a direct role for corneal ALDH as a UV-B photoreceptor in this anterior eye tissue has also been proposed (Abedinia et al. 1990).

DNA prepared from transformed stocks of Drosophila melanogaster induces second-step transformations resembling the original. The gross yield of transformants induced by transformed DNA is several times higher than that induced by the original allo-DNA, but much of this high frequency is attributable to a few exceptionally large clusters of transformants among flies treated with transformed DNA. When these large clusters are omitted from the data, the frequency of transformants induced by DNA from transformed stocks is the same as that induced by allo-DNA. The data therefore support the conclusion that the original DNA-induced alterations resulted from the transfer of genetic material capable of indefinite replication.

A study of α-amylase isozyme patterns from gibberellin-induced endosperms of wheat-alien genotypes (amphiploid, addition and substitution lines) resolved by flat-bed isoelectric focusing identified homoeoloci for α-Amy-1 (malt α-AMY-1 genes) on chromosomes 6H of Hordeum vulgare, 6RL of Secale cereale, 6Rm of S. montanum and 6E of Agropyron elongatum. Homoeoloci for α-Amy-2 (green α-AMY-2 genes) were identified on chromosomes 7HchL of Hordeum chilense, 7RL of Secale cereale, 7Sb of Aegilops bicornis, 7U of Ae. umbellulata and 7EL of Agropyron elongatum. Analysis of mature grain β-amylase identified β-Amy-1 loci on chromosomes 4H of H. vulgare, 4Hch of H. chilense, 4S1 of Ae. sharonensis and Ae. longissima and β-Amy-2 loci on chromosomes 5RL of S. cereale and 5U of Ae. umbellulata. These gene locations provide further evidence for the homoeology of the alien chromosomes with wheat and for the conservation of gene synteny among wheat and its relatives.

Weak but statistically significant sexual isolation has been demonstrated among Vetukhiv's six experimental populations of Drosophila pseudoobscura, all originally descended from founders taken from cultures of the same hybrids from four geographic localities. These six populations were maintained separately for almost 4½ years and then tested for the existence of sexual isolation. The sexual isolation has arisen in the absence of any selection for isolation, evidently as a by-product of genetic divergence.

Genet. Res., Camb. (1986), 47, pp. 83–91

Structural Genes for Phosphatases in Aspergillus nidulans

A labelling error caused nimD-4 to be substituted for nimQ-20. The nim locus shown in Fig. 3 (p. 88) is nimQ not nimD. The genotypes of strains given in the legend to Fig. 3 should read nimQ-20 in place of nimD-4.

The distribution of heterochromatic regions in the chromosomes of diploid, tetraploid and hexaploid wheat shows that the B genome possesses characteristic large blocks. Though analyses of probable B genome donors indicate that Aegilops speltoides has a pattern of distribution of heterochromatin nearest to the B genome chromosomes, a polyphyletic origin of tetraploid wheat seems more plausible.

The Luria-Latarjet effect is an increase in resistance of a virus to DNA damage during infection of a host. It has often been assumed to involve recombinational repair, but this has never been demonstrated experimentally. Using nine bacteriophage (phage) T4 mutants, I present evidence indicating that, for phage T4, the Luria-Latarjet effect is due to three repair pathways-excision repair, post-replication-recombinational-repair (PRRR) and multiplicity reactivation (MR) (a second form of recombinational repair). The results also show that the Luria-Latarjet effect develops in two stages. The first stage starts soon after infection. Damage which occurs during the first stage can be repaired by excision repair or PRRR. The second stage appears to start after the first round of DNA replication is complete. DNA damage which occurs during this stage can apparently be repaired by MR as well as the other two repair pathways. The results of this study support the hypothesis that recombinational repair has been selected to ensure that the progeny phage genomes which are packaged have minimum DNA damage. Since other viruses which infect bacterial, animal and plant cells show a Luria-Latarjet effect similar to that in phage T4, the conclusions from this study may have wide applicability.

Extrachromosomal streptomycin and tetracycline resistance in Staphylococcus aureus E169 has been transduced to three different recipients. An analysis of the transductants demonstrates that: (1) in most cases the behaviour of the markers in the transductants is similar to that in the donor; (2) the markers are co-transduced at frequencies of 2–44% and the frequency is highest when the selected marker is streptomycin resistance; (3) in the co-transductants the markers segregate independently, suggesting that they are unlinked.

Translocation T(III–VIII) in Aspergillus nidulans has been analysed by the detection of meiotic linkage between markers previously located separately on linkage groups III and VIII. The breakage points have been mapped by the detection of linkage between the crinkled type and genetic markers in the region of the break. A segment from linkage group III, approximately 43 units long and including the markers moC96, sC12, sA1 and cnxH3, has been translocated into linkage group VIII. The breakage point is between su6proA and moC96 and the attachment point is close to cha in linkage group VIII. It seems probable that the segment has been inserted into linkage group VIII.

The level and distribution of genetic variability within and among Metrosideros polymorpha populations along altitudinal gradients on the island of Maui, Hawaii were examined to assess the extent of genetic differentiation. Sixteen loci encoding 11 enzymes were scored in 17 populations along the NE wet slope of Mt. Haleakala and Kipahulu Valley in East Maui and six populations along the Puu Kukui trail in West Maui. On average, 50% of the loci were polymorphic within populations with an overall mean of 2·15 alleles per locus. The observed heterozygosities for different populations were moderate (0·108–0·220) and conformed to panmixia except for one of the mid-elevation populations. The distribution of allozyme variation indicates that very little differentiation has occurred along altitudinal gradients. Approximately 90% of the total variation resides within populations in East Maui while 95% was found within West Maui populations. The mean populational pair-wise genetic identities (Nei's I) ranged from 0·909 to 0·998. The UPGMA cluster analysis on genetic identity matrices and PCA on allele frequencies revealed marginal altitudinal differentiation. Twenty one alleles out of a total 63 showed statistically significant correlations with environmental variables.