The genetics of dopa decarboxylase in Drosophila melanogaster. III. Effects of a temperature sensitive dopa decarboxylase deficient mutation on female fertility

The mutation Ddc^ts1 effects female sterility when homozygous, hemizygous, or heterozygous over a series of Ddc null alleles (Ddc^x) indicating that some aspect of Ddc gene function is necessary for female fertility. Ovary transplant experiments demonstrate that the female sterility phenotype is ovary autonomous. Two to 3% of the total DDC activity measurable in newly hatched females is localized in their previtellogenic ovaries. The degree to which females heterozygous for Ddc^ts1 over different Ddc null alleles are fertile at 22°C reflects a continuous spectrum of allelic complementation similar to that observed for the effects of these genotypes on viability at 30°C. Fertility of all the Ddc^ts1/Ddc^x females tested is significantly depressed at 30 vis-a-vis 22°C providing evidence that it is the DDC enzyme activity itself which is required for female fertility. Ddc^ts1/Ddc^ts1 homozygous and Ddc^ts1/Df hemizygous females are nonconditionally, completely sterile at 18, 20, 22, 25, and 30°C. Although all homo- and hemizygous females do lay some eggs, no evidence of embryogenesis or fertilization has ever been detected. The absolute, nonconditional sterility of Ddc^ts1 homo- and hemizygous females stands in stark contrast to the conventional temperature dependent effects of these same genotypes on viability and to the temperature sensitive effects of Ddc^ts1/Ddc^x heterozygous females on both fertility and viability. Reasons for these tissue-specific and genotypic differences are discussed.     

Incidence of XO mice after x-irradiation of spermatogonia

Summary Tabby male mice (X ^Ta Y) were irradiated with 600 R of X-rays and mated in the post-sterile period to untreated C 3 H females (X ⁺ X ⁺). The incidence of XO females after X-irradiation of the spermatogonia was not significantly different from the rate found in the control series. The phenotype of these exceptional females indicates that they are patroclinous XO females. Chromosome counts performed on bone-marrow show that most of the cells have 39 chromosomes as compared to 40 found in the controls.     

Mapping of anH-2-linked gene that influences mating preference in mice

In mating tests of B6 males, and of congenic B6-T1a^a males, with paired B6 and B6-T1a^a females, there was a preponderance of matings with B6-Th1a^a females in both cases. These results conform to a hypothesis that in theQa-T1a region there is anRi (recognition of identity) gene which is expressed in females and influences mating preference; and that anotherRi gene, expressed in males and also influencing mating preference, is situated elsewhere in the MHC region.Abbreviations according to Yamazakiet al. (1978)     

Sterilizing Effect of the Mutant Allele sbr 10 (l(1)ts403) in Compound with Null Allele in Drosophila melanogaster Females

In females of Df(1)v-L4/+(0/+) genotype, the presence of the wild-type allele ofsmall bristles (sbr) gene in a single dose has no significant effect on their fecundity, whereas a reduced dose of the temperature-sensitive allele sbr ¹⁰ (l(1)ts403) causes a strong sterilizing effect in females Df(1)v-L4/sbr ¹⁰ (0/sbr ¹⁰) at permissive temperature. We studied the contribution to this effects of the following factors: resorption of egg chambers, decreased oviposition, offspring death at the embryonic and larval stages, and reduced fecundity in females 0/sbr ¹⁰. Sterilizing effect of the mutant sbr ¹⁰ allele proved to be primarily caused by offspring lethality at the embryonic and first-instar larval stages. In 0/+ females, the majority of undeveloped eggs contained embryos that perished at the late developmental stages, whereas in females 0/sbr ¹⁰, at least 50% of undeveloped egg showed no visible signs of development or the embryo development was arrested at early stages of embryogenesis. The results obtained suggest insufficiency of the temperature-sensitive allele sbr ¹⁰ in haploid state to ensure the reproductive functions of Drosophila melanogaster females.     

Semidominant Effect of the l(1)ts403 (sbr 10) Mutation on Sex Chromosome Nondsjunction in Meiosis in Drosophila melanogaster Females Exposed to Heat

The sbrgene of Drosophila melanogasterbelongs to the NXF(nuclear export factor) family responsible for the mRNA transport from nucleus to cytoplasm. We have shown that in the heat-exposed (37°C, 1 h) females, the l(1)ts403(sbr ¹⁰) mutation leads, in particular, to the high-frequency nondisjunction and loss of sex chromosomes in meiosis. For this trait, the incomplete dominance of the sbr ¹⁰ mutation is observed. At the same time, the sbr ¹⁰ mutation is recessive for many other traits of the heat-exposed flies: reduced viability, low fertility, impaired synthesis of the heat shock proteins, etc. The females heterozygous for the null allele (Df(1)v ^L4, a deletion eliminating gene srb) do not differ from females homozygous for the wild-type allele in frequency of the heat shock-induced nondisjunction and loss of sex chromosomes in meiosis. Because of this, the sbr ¹⁰ mutation can be assigned to the gain-of-function alleles (those gaining the dominance function). Expression of the mutant sbr ¹⁰ allele against the background of the wild-type allele suggests that in the heat shock-exposed females, the heat-modified product of this ts allele has an active effect on sex chromosome disjunction in meiosis.     

The gene fl(2)d is required for various Sxl-controlled processes in Drosophila females

Summary In Drosophila melanogaster, the gene Sex-lethal (Sxl) controls the processes of sex determination, dosage compensation, oogenesis and sexual behaviour. The control of Sxl is by alternative splicing of its primary RNA. We have identified a gene, female-lethal-2-d (fl(2)d), which is needed for the female-specific splicing of Sxl RNA and which also has a vital function independent of Sxl. Here we analyse other aspects of the gene fl(2)d. Specifically, we have analysed the effect of the temperature-sensitive mutation fl(2)d ¹ on the viability of adult flies homozygous for this mutation. We have found that the viability of the mutant females is reduced, while that of the mutant males is not affected. In addition, the capacity of the mutant females to be inseminated is considerably reduced, whilst all the mutant males are able to inseminate females. These effects on females are suppressed by Sxl ^M1. However, the fat body cells of fl(2)d ¹ homozygous females are able to synthesize yolk proteins at the restrictive temperature. We have also carried out, in males, a clonal analysis of fl(2)d ², a mutation lethal in both sexes. We have found that the clones are fully viable. We conclude that the gene fl(2)d seems to be necessary during the adult life of females for the processes that require Sxl ⁺ activity. Moreover, the Sxl-independent vital function of fl(2)d seems to be required in both sexes only during larval development. Offprint requests to: L. Sánchez     

Suppression of distinct ovo phenotypes in the Drosophila female germline by maleless− and Sex-lethalM

Mutations in ovo result in several different phenotypes, which we show are due to the regulation of distinct developmental pathways. Two X (female) germ cells require ovo⁺ activity for viability, but 1X (male) germ cells do not. In our study, we observed suppression of the ovo germline-lethality phenotype in loss-of-function maleless (mle) females indicating that ovo⁺ and mle⁺ have opposing effects in female germ cells; or that they are hierarchically related. Gain-of-function Sex-lethal (Sxl) alleles and male specific lethal-2 alleles did not suppress the ovo germline death phenotype. Many of the surviving germ cells in females mutant for both ovo and mle showed ovarian tumors. In contrast to the germline viability phenotype, we did observe suppression of the tumor phenotype in females heterozygous for gain-of-function alleles of Sxl. Further, females mutant for some hypomorphic ovo alleles were rendered fertile by Sxl gain-of-function alleles. Thus, ovo⁺ is required for at least two distinct functions, one involving mle⁺, and one mediated by Sxl⁺ gene products. The existence of ovo⁺ functions independent of mle⁺ and Sxl⁺ is likely. Dev. Genet. 23:335–346, 1998. © 1998 Wiley-Liss, Inc.     

Effect of Beauveria bassiana on the ovarian development and reproductive potential of Anastrepha ludens (Diptera: Tephritidae)

We investigated the virulence of a native strain of Beauveria bassiana on the mortality, ovarian development, oogenesis, survival, fecundity and fertility of 4-, 8- and 12-day-old Anastrepha ludens females. In the first study, this strain caused 85% mortality in 8-day-old treated females, with a median lethal concentration (LC₅₀) of 3.1×10⁸ (2.1×10⁸–4.7×10⁸) conidia/mL and a median lethal time (LT₅₀) of 6.5 days. In the second study, the ovarian development and oogenesis of A. ludens females treated with 1×10⁹ conidia/mL were monitored daily in sacrificed flies. The fungus infection did not significantly affect ovarian development of the treated females, although there was a delay in vitellogenesis and a reduction in the quantity of mature basal oocytes and oviposition index in these flies. Moreover, the lowest net fecundity was found in 4-, 8- and 12-day-old treated females, and reduced fertility was observed in 4-day-old treated females. An application to test the potential use of this strain under field conditions is discussed.     

Effect of the apterous 56f mutation on N -acetyltransferase and alkaline phosphatase activities in Drosophila melanogaster females

Alkaline phosphatase (AP) and N-acetyltransferase (NAT) activities were studied in 1-day-old Drosophila melanogaster females of the apterous ^56f (ap ^56f ) strain, having an decreased level of the juvenile hormone (JH) and a increased level of dopamine as a result of the mutation, and in the Canton S ancestral wild-type strain in the normal conditions and upon an experimental increase in JH titer. The AP and NAT activities in ap ^56f females were significantly lower than in Canton S females in the norm. JH application increased the AP activity of mutant females to the level characteristic to JH-treated wild-type females. Original Russian Text ? E.V. Bogomolova, N.V. Adonyeva, N.E. Gruntenko, I.Yu. Rauschenbach, 2008, published in Genetika, 2008, Vol. 44, No. 5, pp. 710–712.     

MeCP2 R168X male and female mutant mice exhibit Rett‐like behavioral deficits

Rett syndrome (RTT) is a regressive developmental disorder characterized by motor and breathing abnormalities, anxiety, cognitive dysfunction and seizures. Approximately 95% of RTT cases are caused by more than 200 different mutations in the X‐linked gene encoding methyl‐CpG‐binding protein 2 (MeCP2). While numerous transgenic mice have been created modeling common mutations in MeCP2, the behavioral phenotype of many of these male and, especially, female mutant mice has not been well characterized. Thorough phenotyping of additional RTT mouse models will provide valuable insight into the effects of Mecp2 mutations on behavior and aid in the selection of appropriate models, ages, sexes and outcome measures for preclinical trials. In this study, we characterize the phenotype of male and female mice containing the early truncating MeCP2 R168X nonsense point mutation, one of the most common in RTT individuals, and compare the phenotypes to Mecp2 null mutants. Mecp2^R168X mutants mirror many clinical features of RTT. Mecp2^R168X/y males exhibit impaired motor and cognitive function and reduced anxiety. The behavioral phenotype is less severe and with later onset in Mecp2^R168X/+ females. Seizures were noted in 3.7% of Mecp2^R168X mutant females. The phenotype in Mecp2^R168X/y mutant males is remarkably similar to our previous characterizations of Mecp2 null males, whereas Mecp2^R168X/+ females exhibit a number of phenotypic differences from females heterozygous for a null Mecp2 mutation. This study describes a number of highly robust behavioral paradigms that can be used in preclinical drug trials and underscores the importance of including Mecp2 mutant females in preclinical studies .     

Murine complement factor B (BF) Sexual dimorphism and H-2-Linked polymorphism

Polymorphism of murine BF is described using agarose gel electrophoresis of EDTA-plasma. The proteins were blotted onto cellulose nitrate sheets and BF was detected by incubation of these sheets with anti-BF serum, anti-IgG serum, and ¹²⁵I-labeled protein A successively. After autoradiography, four or five main BF bands were found in plasma of male mice. The strain WLL/BrA (H-2 ^bs carried a more anodal variant than the strains 020/A (H-2 ^pz , B10 (H-2 ^b , B10.A (H-2 ^a , B10.M (H-2 ^f ), and OIR (H-2 ^q ). In backcross and F₂ generations the BF variants always cosegregated with the H-2 haplotypes. In this way linkage to H-2 could be established. When the electrophoretic BF patterns of males and females were compared, a sexual dimorphism was discovered; the females of each strain had only three main BF bands compared with the four or five found in males. However, no differences in level between males and females could be detected, probably because the three BF bands in the females were stronger. These data extend the information on the interspecies homology of the MHC and may open new possibilities for studies of the genetic organization and hormonal regulation of the H-2 complex.     

Non mendelian female sterility in Drosophila melanogaster, further data on chromosomal contamination

Summary In relation to non Mendelian female sterility, Drosophila melanogaster strains can be divided into two main classes, inducer and reactive. The genetic element responsible for the inducer condition (I factor) is chromosomal and may be linked to any chromosome of inducer strains. Each chromosome carrying the I factor (i ⁺ chromosome) can produce females (denoted SF ) showing more or less reduced fertility when introduced by paternal gametes into reactive oocytes. The amount of fertility reduction of SF females depends chiefly on the level of reactivity of their reactive mother i.e. on the particular state of the cytoplasm in the oocytes from which they are issued. As long as i ⁺ chromosomes are transmitted through heterozygous males with reactive originating chromosomes (r chromosomes), the I factor strictly follows Mendelian segregations. In contrast, in heterozygous i ⁺/r females, a varying proportion of r chromosomes may acquire irreversibly I factor, independently of classical genetic recombination, by a process denoted chromosomal contamination. The contaminated r chromosomes behave like i ⁺ chromosomes.The experiments reported in this paper show that chromosomal contamination is a chance event which arises independently in individual r chromosomes. r chromosomes may differ in their ability to be contaminated and there is a systematic difference between chromosomes X and 2. In addition, it is demonstrated that the efficiency of contamination increases with the level of reactivity of the mothers of SF females and therefore is closely correlated with the amount of fertility reduction of SF females.     

Low crowding threshold for induction of sexual reproduction and diapause in a Patagonian rotifer

1. This study investigates the basis and ecological significance of the extremely high propensity for mixis (sexual reproduction) observed in laboratory populations of Brachionus calyciflorus from a temporary pond in Patagonia. 2. Experiments with stem females hatched from resting eggs showed that these females were exclusively amictic but produced mictic daughters even at very low population densities. In six experiments, newly hatched stem females were cultured individually in different volumes (1.5, 12, 40 and 150 mL). The percentage of mictic daughters (mixis ratio) was high in the smaller volumes (e.g. 44–83% in 1.5 mL) and lower in the largest volume (6–21% in 150 mL). A regression analysis combining the data from these experiments showed a highly significant decrease in mixis ratio with volume and indicated that the lowest population density at which mixis still occurs (mixis threshold) would be 3.4 females L^?1 (95% CL 2.9–4.0 females L^?1). This value is considerably lower than mixis thresholds for other rotifers (25–250 females L^?1 for many species and 9000–477 000 females L^?1 for some Spanish Brachionus plicatilis). 3. In three additional experiments, stem females and their amictic daughters were cultured individually in 150 mL. The percentage of mictic daughters produced by these two generations of females was not significantly different, showing that the mixis response to crowding is not inhibited in the stem‐female generation. 4. Laboratory experiments showed that two common predators of the Patagonian B. calyciflorus (the calanoid copepod Parabroteas sarsi and the backswimmer Notonecta vereertbruggheni) each ate 60–70 B. calyciflorus predator^?1 per day and cleared all rotifers from c. 250 mL per day. Thus, a very low mixis threshold and high maximal mixis ratio may ensure production of some resting eggs soon after colonisation of the pond and before complete removal from the plankton. 5. Two laboratory experiments showed that resting eggs of the Patagonian B. calyciflorus hatched at variable rates (28 and 81%) after a brief diapause when kept in the conditions under which they were produced and oviposited (20–21 °C; L: D 16: 8). Early hatching of resting eggs from pond sediment may allow multiple periods of colonisation and resting egg production in a season. This may offset the fitness cost of limited population growth through female parthenogenesis in the face of unpredictable and abrupt risk of extinction because of predators.     

GENETICS OF MIMICRY IN THE TIGER SWALLOWTAIL BUTTERFLIES,PAPILIO GLAUCUS AND P. CANADENSIS (LEPIDOPTERA: PAPILIONIDAE)

The tiger swallowtail butterfly, Papilio glaucus, exhibits a female-limited polymorphism for Batesian mimicry; the Canadian tiger swallowtail, Papilio canadensis, lacks the mimetic (dark) form entirely. The species hybridize to a limited extent where their ranges overlap. Field collections and censuses indicate that mimetic females occur throughout the range of P. glaucus but at lowest frequencies in populations at the latitudinal edges of its geographic range such as the southernmost part of Florida and along the entire northern edge of its distribution from Massachusetts to Minnesota. Frequencies of mimetic females have remained relatively stable over time. Inheritance of the mimetic form is controlled primarily by two interacting sex-linked loci. The typical matrilineal pattern of inheritance in P. glaucus can be explained by polymorphism at a Y-linked locus, b. Analysis of P. glaucus × P. canadensis crosses has also revealed an X-linked locus, s, which controls the expression of the mimetic phenotype. The P. canadensis allele, s^can, suppresses the mimetic phenotype in hybrid and backcross females. Results from more than 12 yr of rearing tiger swallowtails, including interspecies hybrids, indicate that the absence of mimetic P. canadensis females is due to both a high frequency of the “suppressing” allele s^can and low frequency of the black-pigment-determining b + allele. The frequency of s^can (or other suppressing alleles of s) in P. glaucus populations outside the hybrid zone is low. Some males heterozygous at the s locus and some suppressed mimetic females occur within the hybrid zone. A simple genetic model predicts the frequency of daughters that differ in phenotype from their mothers.     

Sex determination and phenotype in wood lemmings with XXY and related karyotypic anomalies

Summary The wood lemming, Myopus schisticolor, possesses a unique sex determining system comprising both XX and XY females. Normal female development in the presence of XY is guaranteed by a mutation on the X, apparently associated with a structural rearrangement in Xp. This mutation inactivates the testis-inducing and male-determining factor on the Y and distinguishes X^* from X, and X^*Y females from XY males. Normal fertility of X^*Y females is ensured by a mitotic (double) nondisjunction mechanism which, at an early fetal stage, eliminates the Y from the germ line and replaces it by a copy of the X^*.Numerical sex chromosome aberrations are not infrequent and the trisomics XXY and X^*XY are relatively common. XXY individuals are sterile males with severe suppression of spermatogenesis. Among X^*XY animals, both males and females, as well as a true lateral hermaphrodite have been observed. Primary deficiency of germ cells, impairment of spermatogenesis and sterility are characteristic traits of the X^*XY males, whereas X^*XY females have normal oogenesis and are fertile. Both these extremes (except female fertility) coexist in the true hermaphrodite described in the present study. These apparently contradictory observations are explainable under the assumption that X^* and X in X^*XY individuals are inactivated non-randomly or that the cells are distributed unequally. Inactivation of the X or X^* determines whether or not the H-Y antigen will be expressed. When comparing conditions in Myopus and in man, an additional assumption has to be made in relation to the gene(s) involved in sex determination, located in Xp:In Myopus they do not escape inactivation, whereas in man they have been claimed to remain active.     

Interaction between sexes and between different circadian phenotypes affects lifespan in the fruit fly Drosophila melanogaster

Circadian clocks regulate the daily temporal structure of physiological and behavioural functions. In the fruit fly Drosophila melanogaster Meigen, disruption of daily rhythms is suggested to reduce the fly's lifespan. In the present study, because pairs of mixed‐sex flies are known to show an activity pattern different from that of individual flies, this hypothesis is tested by measuring the lifespan of flies housed same‐sexually or mixed‐sexually under an LD 12 : 12 h photocycle at a constant temperature of 25 °C. The effect of housing wild‐type (Canton‐S) flies with period (per) circadian clock mutant flies is also examined because the mutant flies have different daily activity patterns. When males and females of wild‐type flies are housed together, their lifespan is substantially lengthened (males) or shortened (females) compared with same‐sex housed flies. The shortening of the lifespan in females is significantly enhanced when mated with per mutant males. The shortening effects are significantly reduced when the mixed‐sex interaction is limited for the first 5 days after emergence. A slight elongation in lifespan, rather than a reduction, occurs when wild‐type females are housed same‐sexually with per⁰ or per^L mutant flies. In male flies, the elongation of lifespan occurs not only when wild‐type males are housed with wild‐type, per⁰ or per^L females, but also when housed with per⁰ or per^S mutant males. Mixed‐sex couples always show altered daily locomotor rhythms with an enhanced night‐time activity, whereas same‐sex couples show daily behavioural profiles slightly altered but essentially similar to a sum of the respective two flies. No significant correlation is found between the lifespan and reproductive capacity. These results suggest that the alteration of daily activity rhythms and sexual interaction may have significant impact on the fly's lifespan.     

Gonads annual development of Kelee shad, <Emphasis Type="Italic">Hilsa kelee</Emphasis> (Cuvier, 1829) from the coastal waters of Pakistan and its spawning ecology

Annual reproductive cycle and spawning ecology of Kelee shad, Hilsa kelee were studied. The sex ratios did not exhibit as 1: 1; whereas 69.19% were females. On the basis of histological examination, the maturity of female gonads of H. kelee was categorized in eight developmental stages: immature, developing, fully developed, hydrated, running ripe, partially spent, spent and post spawning. Whereas males of this species were categorized in five developmental stages: immature, developing, ripe, partially spent and spent. This fish is repeatedly spawner and spawns twice per year: in April to June and August to October. The values of exponent b in the length weight regressions (W = al ^b ) slightly varied in males b = 3.133, R ² = 0.96 and P < 0.01 and females b = 3.143, R ² = 0.95 and P < 0.001. The linear regressions of length-weight relationships were significant for both males and females.     

Some biological parameters of the Mediterranean sand smelt Atherina (Atherina) hepsetus, Linnaeus, 1758 (Pisces: Atherinidae) from the middle eastern Adriatic (Croatian coast)

Data on the length–weight relationship, age, growth, sex ratio and mortality were analysed for the Mediterranean sand smelt, Atherina (Atherina) hepsetus L. (total = 2805; males = 1258; females = 1547) collected in the eastern middle Adriatic island area during the reproductive period (February to April) in 2002. The total length of sampled specimens ranged from 3.8 to 14.5 cm and the weight from 0.28 to 22.39 g. The overall sex ratio was 1.23 : 1 in favour of females, significantly different from the expected 1 : 1 ratio (χ² = 29.76; P < 0.05). All individuals >13.4 cm were females. The oldest collected male and female specimens were 5 years old. The von Bertalanffy growth formula was estimated for females (L_∞ = 15.79 (1−e^{−0.43(t+0.049)}) and males (L_∞ = 15.25 (1−e^{−0.43(t+0.018)}). The power values (b) of the length–weight relationship were very similar for both sexes (b = 3.14) and indicated a slightly allometric growth. The instantaneous rates of mortality for all collected fish were Z = 1.44 year⁻¹; M = 0.94 year⁻¹ and F = 0.50 year⁻¹. The exploitation ratio was E = F/Z = 0.35. The value for M is highly uncertain, however, as well as those values for F and E.     

Age,growth and mortality of invasive sharpbelly,Hemiculter leucisculus (Basilewski, 1855) in Erhai Lake,China

The sharpbelly Hemiculter leucisculus, an invasive species, has expanded its range throughout much of Asia and into the Middle East. However, little is known of its adaptive changes regarding life history traits such as age, growth and mortality that could possibly explain its success as an invasive species. A detailed study of the invasive sharpbelly was conducted based on 4539 samples collected from July 2009 to June 2011 in Erhai Lake, China. Standard length ranged from 4.3–19.1 cm for females and 4.6–12.3 cm for males. Length–weight relationships for females and males were significantly different and described as W = 0.0076SL^3.2608 and W = 0.0084SL^3.1901, respectively. Otoliths are ideal for age determination because of the single annulus formed each year. Based on marginal increment analysis, the total mean CV for age estimate between two readings was 3.55%. The von Bertalanffy growth curves computed by observed length‐at‐age data were expressed as L_t = 25.6 (1 ? e^{?0.176 (t + 1.347)}) for females and L_t = 16.4 (1 ? e^{?0.354 (t + 0.819)}) for males. According to the age, growth and mortality data, there are three possible reasons for H. leucisculus attaining such dominance within a short time in Erhai Lake. First, because of the simple age structure of this species: 97.58% of males were 1–2 years old with a maximum age of only 3 years; 93.14% of females were 1–3 years old, with a maximum age of 6 years. Second, females grew larger than males at any age. Third, instantaneous mortality rates were much higher for males (4.22 year^?1) than for females (1.17 year^?1).     

Genetic characterization of the mei-41 locus in Drosophila melanogaster

Summary The mutagen-sensitive mutant mus(1)104 ^D1 of Drosophila melanogaster maps to a position on the X chromosome very close to the meiotic mutant mei-41 ^D5 . Both mutants have been characterized as mutagen-sensitive and defective in post-replication repair. In the present report we show by complementation studies that mus(1)104 and mus(1)103 are allelic with mei-41. In addition, two reported alleles of mus(1)104 lie between the mei-41 alleles A10 and D5. The size of the mei-41 locus is estimated to be about 0.1 centimorgans (cM). Because several alleles of mei-41 have been shown to reduce recombination and increase meiotic chromosome loss and nondisjunction, mus(1)104 ^D1 females were examined for defects in meiosis. Although there was no evidence for reduced recombination on the second chromosome in homozygous mus(1)104 ^D1 females, heterozygous mus(1)104 ^D1 /mei-41 ^>D5 and mus(1)104 ^D1 /deficiency females showed reduced levels of recombination. However, there was no evidence of an increase in nondijunction in these females.We dedicate this article to the memory of Larry Sandler, who passed away suddenly on February 7, 1987