Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “STERILITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,261 records · Page 70Linked to original sources
PubMed1980

Explanation of sterility in txty male mice.

The lethal 't alleles' of the T complex on mouse chromosome 17 (refs 1, 2) have been assigned to six complementation groups (the definitive classes being t0, t9, t12, tw1, tw5 and tw73), each causing embryonic death at a particular stage. Intercomplementation heterozygotes (txty) show 'partial' complementation, so that only some txty offspring survive. These survivors appear morphologically normal; indeed the females, being fertile, seem entirely normal. The txty males, however, are sterile. Among the reasons given for this sterility in some txty males are low motility of the txty spermatozoa, and an inability to effect fertilization either in vitro or in vivo even when already present at the site of fertilization. Spermatozoa from sterile txty males were reported to be apparently present in 'normal' numbers in the uterus, although actual ejaculate numbers have not been quoted for these, or indeed for normal fertile males. In the human, typical ejaculate counts of less than 20 x 10(6) spermatozoa, where the normal ejaculate contains 100-250 x 10(6), are judged to indicate clinical sterility. The comparison of numbers of spermatozoa10 ejaculated into the female tract by sterile t6tw5, t6tw32 and tw5tw32 (all 'strong' mutations2) and control mice clearly shows an even greater oligozoospermia (about 100 times less than controls) occurring in the txty males.

Animals↗
PubMed1993

Transposon tagging of a male sterility gene in Arabidopsis.

Transformation of the well-studied maize transposable elements into other plant species should enable transposon tagging methodology to be used for the isolation of interesting genes in the heterologous host. Here we describe the isolation of a transposon-tagged male sterile mutant in Arabidopsis thaliana using the maize Enhancer-Inhibitor transposable element system introduced into Arabidopsis. The mutant lacks pollen, preventing normal self-fertilization, a characteristic important for production of hybrid seed in many crop plants. We have identified an Enhancer-transposase-mediated Inhibitor element insertion responsible for the male sterile phenotype, and isolated the corresponding gene named MALE STERILITY 2. Critical evidence that the Inhibitor-element-containing gene is involved in the male sterile phenotype is provided by the DNA sequences of new excision-derived alleles from independent stable fertile and male sterile progeny of the original mutant.

Amino Acid Sequence↗
PubMed1991

The evolutionary history of Drosophila buzzatii. XXI. Cumulative action of multiple sterility factors on spermatogenesis in hybrids of D. buzzatii and D. koepferae.

The genetic basis of sterility in male hybrids of Drosophila buzzatii and D. koepferae has been investigated by assessment of the effects on spermatogenesis of substituting separate chromosome segments of the recipient species with the homologous material from the donor species, either in heterozygous (autosomes) or hemizygous (X chromosome) condition, after successive backcrossing of hybrid females to either parental species. Introgressed segments were identified by the characteristic asynapsis of the polytene chromosomes in their heterospecific regions. Except for one case, the introgression of chromosome segments either from autosome 3, 4, or 5 brings about sterility only when the introgressed segment exceeds a minimum size (threshold size). Segments of equal size frequently produce similar abnormalities, whose severity increases with the size of the introgressed segment. Apparently, throughout these autosomes of D. buzzatii and D. koepferae there are many non-allelic, minor sterility genes, whose individual segregation cannot be recognized phenotypically, and which act cumulatively on the same characteristics of spermatogenesis, each contributing a small effect to the phenotype. Accordingly, these genes should be considered as polygenes, and the type of sterility they bring about should be properly designated polygenic sterility.

Animals↗
PubMed1996

Correction of the sterility defect in homozygous obese female mice by treatment with the human recombinant leptin.

The sterility of male and female homozygous ob/ob mice is a recognized feature of the ob mutation (1). Whereas ob/ob males can occasionally reproduce if maintained on a restricted diet, ob/ob females are always sterile (2). Thinning of the ob/ob females to normal weight by diet-restriction failed to correct their sterility. Early sexual development is normal in ob/ob females; however, ovulation never follows and the mice remain prepuberal indefinitely with no occurrence of oestrus cycles. Reproductive hormones are reduced in ob/ob females (3) demonstrating a functional defect from the hypothalamic-pituitary axis (4-6). The ovaries of ob/ob females are capable of producing viable eggs when transplanted into lean female recipients (7). Reconstitution of reproductive functions in the ob/ob female necessitates delivery of hypothalamic extracts to the third ventricle (8) and administration of pituitary extract (9), gonadotropic hormones (10), progesterone (11) and relaxin (12). These previous findings demonstrate that the sterility of ob/ob females is caused by an insufficiency of hormones at the hypothalamic-pituitary level rather than physical hindrance of copulatory activity, pregnancy and parturition caused by excess adipose tissue. We show here that repeated administration of only the recombinant human ob protein, leptin, into homozygous female ob/ob mice can correct their sterility, thus resulting in ovulation, pregnancy and parturition.

Animals↗
PubMed2003

Antisense inhibition of mitochondrial pyruvate dehydrogenase E1alpha subunit in anther tapetum causes male sterility.

We hypothesized that cytoplasmic male sterility (CMS) in sugar beet may be the consequence of mitochondrial dysfunctions affecting normal anther development. To test the hypothesis, we attempted to mimic the sugar beet CMS phenotype by inhibiting the expression of mitochondrial pyruvate dehydrogenase (PDH), which is essential for the operation of the tricarboxylic acid (TCA) cycle. Screening with a cDNA library of sugar beet flower buds allowed the identification of two PDH E1alpha subunit genes (bvPDH_E1alpha-1 and bvPDH_E1alpha-2). bvPDH_E1alpha-1 was found to be highly expressed in tap roots, whereas bvPDH_E1alpha-2 was expressed most abundantly in flower buds. Green fluorescent protein (GFP) fusion of bvPDH_E1alpha revealed mitochondrial targeting properties. A 300-bp bvPDH_E1alpha-1 cDNA sequence (from +620 to +926) was connected to a tapetum-specific promoter in the antisense orientation and then introduced into tobacco. Antisense expression of bvPDH_E1alpha-1 resulted in conspicuously decreased endogenous bvPDH_E1alpha-1 transcripts and male sterility. The tapetum in the male-sterile anthers showed swelling or abnormal vacuolation. It is also worth noting that in the sterile anthers, cell organelles, such as elaioplasts, tapetosomes and orbicules were poorly formed and microspores exhibited aberrant exine development. These features are shared by sugar beet CMS. The results thus clearly indicate that inhibition of PDH activity in anther tapetum is sufficient to cause male sterility, a phenocopy of the sugar beet CMS.

Amino Acid Sequence↗
PubMed1989

[Intra-tubal embryo transfer (IVF/IT-ET) in the treatment of non-tubal-induced sterility. Initial studies of the value of a new and expensive therapy procedure].

Intratubar embryo transfer is a form of sterility treatment, in which the in-vitro-fertilized pre-implantation embryos are transferred into the intact fallopian tube(s). This enables the benefits of in-vitro fertilization (information of the gamete fertilization behavior, specific incubation of dysmature oocytes, reduction of the polyploidy rate, risk of multiple pregnancies) to be combined with those of gamete intrafallopian transfer (GIFT; tubar environment for the further development of the pre-implantation embryos). Intratubar embryo transfer is indicated in cases of sterility that are not due to the fallopian tubes; in addition to idiopathic sterility, particular emphasis is put on a certain form of immunological sterility (antibodies against sperm antigens), which seems to be a special indication for this method. Intratubar embryo transfer demands a two sided approach. It is advisable to collect the oocytes transvaginally, guided by ultrasound, since general anaesthesia maybe dispensed with - if so desired. The embryo transfer itself still requires a pelviscopy, which is only performed once fertilization of the oocyte has been confirmed; which is in contrast to GIFT, in which pelviscopy is an inherent part of each treatment cycle. In spite of this advantage, intratubar embryo transfer is a method, which is associated with a high expenditure. The aim of the study was, to evaluate the success rate when all the alternative, less costly options have been exhausted. Our first results are demonstrating, that intratubar embryo transfer is successful, even as a second line therapy. Therefore the method has a significance in the treatment of sterility, not caused by the tubes and the expenditure, with which it is associated, can be justified.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1981

Identification and characterization of double-stranded RNA associated with cytoplasmic male sterility in Vicia faba.

The cytoplasmic male sterility (CMS) trait of at least one line of Vicia faba plants is always associated with the presence of high molecular weight double-stranded RNA in the leaf tissue extracts. Subcellular fractions of leaf tissue from CMS and fertile maintainer plants were initially analyzed in an attempt to locate, identify, and characterize the genetic material involved with the sterility trait. This CMS-associated high molecular weight RNA was found only in the cytosol of the "447" male sterile line of V.faba plants and could not be isolated from the recurrent parent (maintainer), from lines that had been fertility-restored, or from lines that had reverted from the sterile condition. We have been able to move the CMS-associated RNA from donor to fertile host plants through a dodder bridge. These hots not only contain the RNA but now exhibit a male sterile phenotype, as detected by visual examination of the flower, the pollen, morphological characteristics, and pollen staining ability.

Journal Article↗
PubMed1993

Male-sterility induction in transgenic tobacco plants with an unedited atp9 mitochondrial gene from wheat.

Cytoplasmic male sterility in plants is associated with mitochondrial dysfunction. We have proposed that a nuclear-encoded chimeric peptide formed by mitochondrial sequences when imported into the mitochondria may impair organelle function and induce male sterility in plants. A model developed to test this hypothesis is reported here. Assuming that the editing process in higher plant mitochondria reflects a requirement for producing active proteins, we have used edited and unedited coding sequences of wheat ATP synthase subunit 9 (atp9) fused to the coding sequence of a yeast coxIV transit peptide. Transgenic plants containing unedited atp9 exhibited either fertile, semifertile, or male-sterile phenotypes; controls containing edited atp9 or only the selectable marker gave fertile plants. Pollen fertility ranged from 31% to 75% in fertile plants, 10% to 20% in semifertile plants, and < 2% in male-sterile plants. Genetic and molecular data showed that the chimeric plasmid containing the transgene is inherited as a Mendelian trait. The transgenic protein is imported into the mitochondria. The production and frequency of semifertile or male-sterile transgenic plants conform to the proposed hypothesis.

Amino Acid Sequence↗
PubMed1997

Cell type-specific loss of atp6 RNA editing in cytoplasmic male sterile Sorghum bicolor.

RNA editing and cytoplasmic male sterility are two important phenomena in higher plant mitochondria. To determine whether correlations might exist between the two, RNA editing in different tissues of Sorghum bicolor was compared employing reverse transcription-PCR and subsequent sequence analysis. In etiolated shoots, RNA editing of transcripts of plant mitochondrial atp6, atp9, nad3, nad4, and rps12 genes was identical among fertile or cytoplasmic male sterile plants. We then established a protocol for mitochondrial RNA isolation from plant anthers and pollen to include in these studies. Whereas RNA editing of atp9, nad3, nad4, and rps12 transcripts in anthers was similar to etiolated shoots, mitochondrial atp6 RNA editing was strongly reduced in anthers of the A3Tx398 male sterile line of S. bicolor. atp6 transcripts of wheat and selected plastid transcripts in S. bicolor showed normal RNA editing, indicating that loss of atp6 RNA editing is specific for cytoplasmic male sterility S. bicolor mitochondria. Restoration of fertility in F1 and F2 lines correlated with an increase in RNA editing of atp6 transcripts. Our data suggest that loss of atp6 RNA editing contributes to or causes cytoplasmic male sterility in S. bicolor. Further analysis of the mechanism of cell type-specific loss of atp6 RNA editing activity may advance our understanding of the mechanism of RNA editing.

Cytoplasm↗
PubMed1999

Follicle cell proteasome activity and acid extract from the egg vitelline coat prompt the onset of self-sterility in Ciona intestinalis oocytes.

In the hermaphrodite ascidian Ciona intestinalis, the egg vitelline coat (VC) controls gamete self-nonself discrimination. Oocytes, after germinal vesicle breakdown, can be fertilized by both self and nonself sperm. However, a barrier to fertilization by self sperm progressively develops in the VC in the 3 hours after germinal vesicle breakdown. During this period, follicle cells attached to the outer surface of the VC release self-sterility factors that bind to the VC. Within the follicle cells, these factors (possibly peptides) are thought to be shuttled to the cell membrane by an hsp70 homolog (Cihsp70). In fact, antibodies to hsp70 block the development of self-sterility. Proteasomes are central to the production of antigen peptides. Specific inhibition of proteasome activity with clasto-lactacystin beta-lactone (CLbetaL) prevented the onset of self-sterility, but had no effect once this process had started. CLbetaL did not block fertilization by nonself sperm. The self-sterility factors were removed from mature oocytes by exposure to acidified media, and their biological activity was transferred to immature oocytes treated with CLbetaL. The obvious high multiplicity of self-nonself recognition alleles involved in fertilization, and the involvement of an hsp70 and a proteasome in processing self-sterility factors, suggests that this system may be evolutionarily related to the vertebrate immune system.

Acids↗
PubMed1981

A laboratory study of the persistence of carbofuran and its 3-hydroxy- and 3 keto-metabolites in sterile and natural mineral and organic soils.

In a laboratory study, the persistence of carbofuran and its 3-hydroxy- and 3-keto-metabolites was examined separately over 16 wk in sterile and natural organic (muck) and mineral (loam) soils. Carbofuran was relatively persistent in sterile soils; at 8 wk 77% remained in the sterile muck and about 50% remained in the sterile loam. In the natural muck 25% of initial carbofuran remained at wk whereas in the natural loam carbofuran had completely disappeared by that time. The 3-ketocarbofuran was very short-lived even in the sterile muck where only 50% remained at 1 wk. The 3-hydroxycarbofuran degraded appreciably on zero day in the natural soils (with conversion to 3-keto-carbofuran) and about 90% had disappeared in 1 wk. A more detailed study of the persistence of 3-hydroxycarbofuran in the natural soils showed complete disappearance in 2 days in loam and in 3 days in muck. The 3-ketocarbofuran produced from the 3-hydroxy-carbofuran reached a maximum concentration in 1 day and then disappeared within 4 days in loam and about 1 wk in muck.

Actinomycetales↗
PubMed1993

Sporicidal activity of chemical sterilants used in hospitals.

OBJECTIVE: The current study was designed to assess the sporicidal activity of chemical sterilants using the Association of Official Analytical Chemists (AOAC) sporicidal test. Chemical sterilants are used most commonly in the healthcare setting to disinfect medical instruments such as endoscopes. This study was undertaken to evaluate the efficacy of several newer formulations of glutaraldehydes and hydrogen peroxide as chemical sterilants. DESIGN: Using the AOAC test the following agents were tested: two 2% alkaline glutaraldehydes (2% Alk-Glut), 2% acid glutaraldehyde (2% Acid Glut), 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate, 10% glutaraldehyde-0.5% phenylphenol-0.1% tertiary amylphenol, and 6% hydrogen peroxide (H2O2). Growth in > 1 of 60 seeded penicylinders is considered by the AOAC to indicate failure of sporicidal activity. RESULTS: Test results of the six disinfectants against Bacillus subtilis using the manufacturers' specified use-dilution and exposure time were: 0/60 with 2% Alk-Glut (product 1) at 10 hours, 0/60 with 2% Alk-Glut (product 2) at 8 hours, 0/60 with 2% Acid Glut at 10 hours, 2/60 with 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate at 6.75 hours, 0/60 with a 1:5 dilution (2.0% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylphenol at 6 hours, 59/60 with a 1:20 dilution (0.5% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% tertiary amylphenol at 12 hours and 0/60 with 6% H2O2 at 6 hours. Test results against Clostridium sporogenes were: 2/60 with 2% Alk-Glut (product 1) at 10 hours, 1/60 with 2% Alk-Glut (product 2) at 8 hours, 1/60 with 2% Acid Glut at 10 hours, 2/60 with undiluted 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate at 6.75 hours, 6/60 with a 1:5 dilution (2% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylpenol at 6 hours, 60/60 with a 1:20 dilution (0.5% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylpenol at 12 hours, and 0/60 with 6% H2O2 at 6 hours. Dilutions of 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate yielded the following results against C sporogenes: 59/60 with a 1:8 dilution (0.25% Glut) at 6.75 hours, 60/60 with a 1:16 dilution (0.125% Glut) at 6.75 hours, 11/90 with a 1:8 (0.25% Glut) dilution at 12 hours, and 60/60 with a 1:16 dilution (0.125% Glut) at 12 hours. CONCLUSIONS: Both 2% acid and alkaline glutaraldehydes are effective chemical sterilants. Diluting glutaraldehyde-based sterilants below 2% glutaraldehyde resulted in failure to kill spores of B subtilis and C sporogenes.

Colony Count, Microbial↗
PubMed2003

Evidence for ovarian self-incompatibility as a cause of self-sterility in the relictual woody angiosperm, Pseudowintera axillaris (Winteraceae).

Species within the genus Pseudowintera exhibit high rates of self-sterility. Self-sterility in the genus has been previously posited-but not confirmed-to be the result of late-acting ovarian self-incompatibility (OSI) functioning within nucellar tissue of the ovule to prevent self pollen tubes from entering the embryo sac. Structural and functional aspects of pollen-carpel interactions and early seed development following cross- and self-pollination were investigated in P. axillaris to determine the site, timing and possible mechanisms of self-sterility. No significant differences were observed between pollen tube growth, ovule penetration and double fertilization following cross- and self-pollination. Pollen tubes exhibited phasic growth in an extracellular matrix composed of proteins and carbohydrates, as well as arabinogalactans/arabinogalactan proteins. A uniform failure in embryo sac development prior to division of the zygote was apparent within 15 d following double fertilization by self gametes. Results indicate that SI mechanisms in P. axillaris do not prevent double fertilization from occurring. Instead, mechanisms of self-sterility affect post-zygotic development of the embryo sac. Although self-sterility may be attributed to inbreeding depression, given the post-zygotic nature of failure in embryo sac development, the possibility of late-acting OSI is discussed.

Crosses, Genetic↗
PubMed1987

Genetics of male and female sterility in hybrids of Drosophila pseudoobscura and D. persimilis.

The genetic basis of male and female sterility in hybrids of Drosophila pseudoobscura-Drosophila persimilis was studied using backcross analysis. Previous studies indirectly assessed male fertility by measuring testis size; these studies concluded that male sterility results from an X chromosome-autosome imbalance. By directly scoring for the production of motile sperm, male sterility is shown to be largely due to an incompatibility between genes on the X and Y chromosomes of these two species. These species have diverged at a minimum of nine loci affecting hybrid male fertility. Semisterility of hybrid females appears to result from an X chromosome-cytoplasm interaction; the X chromosome thus has the largest effect on sterility in both male and female hybrids. This is apparently the first analysis of the genetic basis of female sterility, or of sterility/inviability affecting both sexes, in an animal hybridization.

Animals↗
PubMed1993

The genetic basis of Haldane's rule and the nature of asymmetric hybrid male sterility among Drosophila simulans, Drosophila mauritiana and Drosophila sechellia.

Haldane's rule (i.e., the preferential hybrid sterility and inviability of heterogametic sex) has been known for 70 years, but its genetic basis, which is crucial to the understanding of the process of species formation, remains unclear. In the present study, we have investigated the genetic basis of hybrid male sterility using Drosophila simulans, Drosophila mauritiana and Drosophila sechellia. An introgression of D. sechellia Y chromosome into a fairly homogenous background of D. simulans did not show any effect of the introgressed Y on male sterility. The substitution of D. simulans Y chromosome into D. sechellia, and both reciprocal Y chromosome substitutions between D. simulans and D. mauritiana were unsuccessful. Introgressions of cytoplasm between D. simulans and D. mauritiana (or D. sechellia) also did not have any effect on hybrid male sterility. These results rule out the X-Y interaction hypothesis as a general explanation of Haldane's rule in this species group and indicate an involvement of an X-autosome interaction. Models of symmetrical and asymmetrical X-autosome interaction have been developed which explain the Y chromosome substitution results and suggest that evolution of interactions between different genetic elements in the early stages of speciation is more likely to be of an asymmetrical nature. The model of asymmetrical X-autosome interaction also predicts that different sets of interacting genes may be involved in different pairs of related species and can account for the observation that hybrid male sterility in many partially isolated species is often nonreciprocal or unidirectional.

Animals↗
PubMed1993

A combined classical genetic and high resolution two-dimensional electrophoretic approach to the assessment of the number of genes affecting hybrid male sterility in Drosophila simulans and Drosophila sechellia.

We have attempted to estimate the number of genes involved in postzygotic reproductive isolation between two closely related species, Drosophila simulans and Drosophila sechellia, by a novel approach that involves the use of high resolution two-dimensional gel electrophoresis (2DE) to examine testis proteins in parents, hybrids and fertile and sterile backcross progenies. The important results that have emerged from this study are as follows: (1) about 8% of about 1000 proteins examined showed divergence (presence/absence) between the two species; (2) by tracing individual proteins in parental, hybrid and backcross males, we were able to associate the divergent proteins with different chromosomes and found that most divergent proteins are associated with autosomes and very few with X chromosome, Y chromosome and cytoplasm; (3) when proteins showing both quantitative and qualitative differences between the two species were examined in F1 hybrid males, most (97.4%) proteins were expressed at levels between the two parents and no sign of large scale changes in spot density was observed. All the proteins observed in the two parental species were present in F1 hybrid males except two species-specific proteins that may be encoded (or regulated) by sex chromosomes; (4) when different fertile and sterile backcross male testes were compared, a few D. sechellia-specific proteins were identified to be consistently associated with male sterility. These results along with the observation that a large proportion (23.6%) of first generation backcross males were fertile show that hybrid male sterility between D. simulans and D. sechellia involves a relatively small number of genes. Role of large scale genetic changes due to general genome incompatibility is not supported. The results also suggest that the large effect of X chromosome on hybrid male sterility is not due to higher divergence of X chromosome than autosomes.

Animals↗
PubMed1994

Evidence for complex genic interactions between conspecific chromosomes underlying hybrid female sterility in the Drosophila simulans clade.

F1 hybrid females between the sibling species Drosophila simulans, Drosophila mauritiana and Drosophila sechellia are completely fertile. However, we have found that female sterility can be observed in F2 backcross females who are homozygous for D. simulans X chromosomes and homozygous for autosomal regions from either D. mauritiana or D. sechellia. Our results indicate that neither D. mauritiana autosome (2 or 3) can cause complete female sterility in a D. simulans background. The simultaneous presence of homozygous regions from both the second and third chromosomes of D. mauritiana, however, causes nearly complete female sterility which cannot be accounted for by their individual effects. The two autosomes of D. sechellia may show a similar pattern. From the same crosses, we also obtained evidence against a role for cytoplasmic or maternal effects in causing hybrid male sterility between these species. Taken with the results presented elsewhere, these observations suggest that epistatic interactions between conspecific genes in a hybrid background may be the prevalent mode of hybrid sterility between recently diverged species.

Animals↗
PubMed1994

Genetics of hybrid male sterility between drosophila sibling species: a complex web of epistasis is revealed in interspecific studies.

To study the genetic differences responsible for the sterility of their male hybrids, we introgressed small segments of an X chromosome from Drosophila simulans into a pure Drosophila mauritiana genetic background, then assessed the fertility of males carrying heterospecific introgressions of varying size. Although this analysis examined less than 20% of the X chromosome (roughly 5% of the euchromatic portion of the D. simulans genome), and the segments were introgressed in only one direction, a minimum of four factors that contribute to hybrid male sterility were revealed. At least two of the factors exhibited strong epistasis: males carrying either factor alone were consistently fertile, whereas males carrying both factors together were always sterile. Distinct spermatogenic phenotypes were observed for sterile introgressions of different lengths, and it appeared that an interaction between introgressed segments also influenced the stage of spermatogenic defect. Males with one category of introgression often produced large quantities of motile sperm and were observed copulating, but never inseminated females. Evidently these two species have diverged at a large number of loci which have varied effects on hybrid male fertility. By extrapolation, we estimate that there are at least 40 such loci on the X chromosome alone. Because these species exhibit little DNA-sequence divergence at arbitrarily chosen loci, it seems unlikely that the extensive functional divergence observed could be due mainly to random genetic drift. Significant epistasis between conspecific genes appears to be a common component of hybrid sterility between recently diverged species of Drosophila. The linkage relationships of interacting factors could shed light on the role played by epistatic selection in the dynamics of the allele substitutions responsible for reproductive barriers between species.

Animals↗