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L W Beukeboom

Publications and source records attributed to L W Beukeboom.

11 recordsLinked to original sources
PubMed2001

Why girls want to be boys.

The mechanisms by which sex is genetically determined are bewilderingly diverse and appear to change rapidly during evolution.(1) What makes the sex-determining process so prone to perturbations? Two recent articles(2,3) explore theoretically the role of genetic conflict in sex determination evolution. Both studies use the idea that selection on sex-determining genes may act differently in parents and in offspring and they suggest that the resulting conflict can drive changes in sex-determining mechanisms.

Animals↗
PubMed2001

Courtship and mating behaviour of interspecific Nasonia hybrids (Hymenoptera, Pteromalidae): a grandfather effect.

Nasonia courtship behaviour includes easily quantifiable, stereotyped components. We analysed displays of N. vitripennis x N. longicornis hybrid males. Most of them performed well-organised displays that were intermediate between the parental species. However, in both reciprocal crosses, a significant bias towards the behaviour of the grandpaternal species was observed. Possible explanations for this effect are a biased recovery of genotypes, either due to nucleo-cytoplasmic interaction or non-mendelian transmission, or differential activation of genes in hybrid females. This study is a first step towards unravelling the genetic architecture of courtship behaviour of Nasonia, which may provide information about factors responsible for species isolation.

Animals↗
PubMed2000

B-chromosome evolution.

B chromosomes are extra chromosomes to the standard complement that occur in many organisms. They can originate in a number of ways including derivation from autosomes and sex chromosomes in intra- and interspecies crosses. Their subsequent molecular evolution resembles that of univalent sex chromosomes, which involves gene silencing, heterochromatinization and the accumulation of repetitive DNA and transposons. B-chromosome frequencies in populations result from a balance between their transmission rates and their effects on host fitness. Their long-term evolution is considered to be the outcome of selection on the host genome to eliminate B chromosomes or suppress their effects and on the B chromosome's ability to escape through the generation of new variants. Because B chromosomes interact with the standard chromosomes, they can play an important role in genome evolution and may be useful for studying molecular evolutionary processes.

Animals↗
PubMed2000

Absence of single-locus complementary sex determination in the braconid wasps Asobara tabida and Alysia manducator.

In species with single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. In the haplodiploid Hymenoptera, sl-CSD results in females, if individuals are heterozygous at the sex locus, and in males, if individuals are hemizygous (haploid males) or homozygous (diploid males). Several hymenopteran species have been shown to have sl-CSD, but in several others sl-CSD is absent and the phylogenetic distribution remains unclear. In the family Braconidae, all four species tested so far were shown to possess sl-CSD. In this study, inbreeding experiments were used to test for the presence of sl-CSD in two species belonging to a subfamily of the Braconidae, Asobara tabida and Alysia manducator (Alysiinae). In both species inbreeding experiments showed no difference in brood size or sex ratio compared to the (outbred) control group. Furthermore, the sex ratios found in the inbreeding treatment differed significantly from the sex ratios expected under sl-CSD. Therefore, we conclude that sl-CSD is absent in these species. This study is the first to show the lack of sl-CSD in species of the Braconidae family and that hymenopteran sex-determining mechanisms can vary, even within a family.

Alleles↗
PubMed2000

Automictic parthenogenesis in the parasitoid Venturia canescens (Hymenoptera: Ichneumonidae) revisited.

Both arrhenotokous and thelytokous reproduction are known to occur in the parasitoid wasp Venturia canescens. The cytological mechanism of thelytoky was previously reported to involve the formation of a restitution metaphase after the reduction division, but the exact nature of the subsequent divisions, whether reductional or equational, remained unclear. We reinvestigated the cytological mechanisms in a thelytokous strain collected in France. Our observations confirm previous results, but an equational and not a reduction division was observed after restitution. This type of reproduction can be classified as central fusion automictic parthenogenesis. In two arrhenotokous strains the normal pattern of oogenesis and syngamy of Hymenoptera was observed. In addition, we used PCR amplification to show that thelytoky in V. canescens is not caused by Wolbachia bacteria. The results are discussed in relation to maintenance of heterozygosity and female sex.

Animals↗
PubMed1996

Is the Y chromosome of Drosophila an evolved supernumerary chromosome?

The Y chromosomes of most Drosophila species are necessary for male fertility but they are not involved in sex determination. They have many puzzling properties that resemble the effects caused by B chromosomes. Classical genetic and molecular studies reveal substantial affinities between Y and B chromosomes and suggest that the Y chromosomes of Drosophila are not degenerated homologues of the X chromosomes, but rather that their Y chromosomes evolved as specialized supernumeraries similar to classical B chromosomes.

Animals↗
PubMed1995

Sex determination in Hymenoptera: a need for genetic and molecular studies.

Sex-determining mechanisms appear to be very diverse in invertebrates. Haplodiploidy is a widespread mode of reproduction in insects: males are haploid and females are diploid. Several models have been proposed for the genetic mechanisms of sex determination in haplodiploid Hymenoptera. Although a one-locus multi-allele model is valid for several species, sex determination in other species cannot be explained by any of the existing models. Evidence for and predictions of two recently proposed models are discussed. Some genetic and molecular approaches are proposed to study sex determination in Hymenoptera.

Alleles↗
PubMed1994

Junctions between repetitive DNAs on the PSR chromosome of Nasonia vitripennis: association of palindromes with recombination.

The Paternal-Sex-Ratio (PSR) chromosome of Nasonia vitripennis contains several families of repetitive DNAs that show significant sequence divergence but share two palindromic regions. This study reports on the analysis of junctions between two of these repetitive DNA families (psr2 and psr18). Three lambda clones that hybridized to both repeat families were isolated from PSR-genomic DNA libraries through multiple screenings and analyzed by Southern blots. Analysis of clones showed a region in which the two repeat types are interspersed, flanked by uniform blocks of each repeat type. PCR amplification of genomic DNA confirmed the contiguous arrangement of psr2 and psr18 on PSR and identified an additional junction region between these repeats that was not present in the lambda inserts. We isolated and sequenced 41 clones from the lambda inserts and genomic PCR products containing junction sequences. Sequence analysis showed that all transitions between psr2 and psr18 repeats occurred near one of the two palindromes. Based on the inheritance pattern of PSR, recombination between repeats on this chromosome must be mitotic (rather than meiotic) in origin. The occurrence of exchanges near the palindromes suggests that these sequences enhance recombination between repeat units. Rapid amplification of repetitive DNA may have been an important factor in the evolution of the PSR chromosome.

Animals↗
PubMed1993

Deletion analysis of the selfish B chromosome, Paternal Sex Ratio (PSR), in the parasitic wasp Nasonia vitripennis.

Paternal Sex Ratio (PSR) is a "selfish" B chromosome in the parasitoid wasp Nasonia vitripennis. It is transmitted via sperm, but causes supercondensation and destruction of the paternal chromosomes in early fertilized eggs. Because this wasp has haplodiploid sex determination, the effect of PSR is to convert diploid (female) eggs into haploid (male) eggs that carry PSR. Characterizing its genetic structure is a first step toward understanding mechanisms of PSR action. The chromosome is largely heterochromatic and contains several tandemly repeated DNA sequences that are not present on the autosomes. A deletion analysis of PSR was performed to investigate organization of repeats and location of functional domains causing paternal chromosome destruction. Deletion profiles using probes to PSR-specific repetitive DNA indicate that most repeats are organized in blocks on the chromosome. This study shows that the functional domains of PSR can be deleted, resulting in nonfunctional PSR chromosomes that are transmitted to daughters. A functional domain may be linked with the psr22 repeat, but function may also depend on abundance of PSR-specific repeats on the chromosome. It is hypothesized that the repeats act as a "sink" for a product required for proper paternal chromosome processing. Almost all deletion chromosomes remained either functional of nonfunctional in subsequent generations following their creation. One chromosome was exceptional in that it reverted from nonfunctionality to functionality in one lineage. Transmission rates of nonfunctional deletion chromosomes were high through haploid males, but low through diploid females.

Animals↗
PubMed1992

Effects of deletions on mitotic stability of the paternal-sex-ratio (PSR) chromosome from Nasonia.

Paternal-Sex-Ratio (PSR) is a B chromosome that causes all-male offspring in the parasitoid wasp Nasonia vitripennis. It is only transmitted via sperm of carrier males and destroys the other paternal chromosomes during the first mitotic division of the fertilized egg. Because of haplodiploidy, the effect of PSR is to convert diploid (female) eggs into haploid eggs that develop into PSR-bearing males. The PSR chromosome was previously found to contain several families of repetitive DNA, which appear to be present in local blocks. PSR chromosomes with irradiation-induced deletions have decreased rates of transmission and increased variation in transmission. This study investigates whether these differences in transmission of deletion chromosomes are due to mitotic instability. Two deletion chromosomes (E306 and F316) and the wild-type PSR chromosome were examined. A cytogenetic assay of testes revealed that wild-type PSR males contained the chromosome in 98%-100% of their spermatocytes. Similar counts from carriers of two deletion chromosomes were lower and varied between individuals from 50%-100%. One F316 male did not contain the chromosome in any of its spermatocytes although the chromosome was present in somatic tissues based on hybridization to PSR-specific repetitive DNA. A molecular analysis of males found the wild-type PSR chromosome to be present in all somatic tissues. Tissue specific differences in the presence of PSR were found in several males from the two deletion lines. The results show that deletions can result in mosaicism due to increased mitotic instability of PSR. Such individuals sometimes partially or completely fail to transmit the chromosome.(ABSTRACT TRUNCATED AT 250 WORDS)

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