| 1. |
- Mozzachiodi, S., et al.
(författare)
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Aborting meiosis allows recombination in sterile diploid yeast hybrids
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Hybrids are often considered evolutionary dead ends because they do not generate viable offspring. Here, the authors show that sterile yeast hybrids generate genetic diversity through meiotic-like recombination by aborting meiosis and return to asexual growth. Hybrids between diverged lineages contain novel genetic combinations but an impaired meiosis often makes them evolutionary dead ends. Here, we explore to what extent an aborted meiosis followed by a return-to-growth (RTG) promotes recombination across a panel of 20 Saccharomyces cerevisiae and S. paradoxus diploid hybrids with different genomic structures and levels of sterility. Genome analyses of 275 clones reveal that RTG promotes recombination and generates extensive regions of loss-of-heterozygosity in sterile hybrids with either a defective meiosis or a heavily rearranged karyotype, whereas RTG recombination is reduced by high sequence divergence between parental subgenomes. The RTG recombination preferentially arises in regions with low local heterozygosity and near meiotic recombination hotspots. The loss-of-heterozygosity has a profound impact on sexual and asexual fitness, and enables genetic mapping of phenotypic differences in sterile lineages where linkage analysis would fail. We propose that RTG gives sterile yeast hybrids access to a natural route for genome recombination and adaptation.
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| 2. |
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| 3. |
- Brindefalk, B., et al.
(författare)
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Bacterial composition in Swedish raw drinking water reveals three major interacting ubiquitous metacommunities
- 2022
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Ingår i: Microbiologyopen. - : Wiley. - 2045-8827. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Background Surface raw water used as a source for drinking water production is a critical resource, sensitive to contamination. We conducted a study on Swedish raw water sources, aiming to identify mutually co-occurring metacommunities of bacteria, and environmental factors driving such patterns. Methods The water sources were different regarding nutrient composition, water quality, and climate characteristics, and displayed various degrees of anthropogenic impact. Water inlet samples were collected at six drinking water treatment plants over 3 years, totaling 230 samples. The bacterial communities of DNA sequenced samples (n = 175), obtained by 16S metabarcoding, were analyzed using a joint model for taxa abundance. Results Two major groups of well-defined metacommunities of microorganisms were identified, in addition to a third, less distinct, and taxonomically more diverse group. These three metacommunities showed various associations to the measured environmental data. Predictions for the well-defined metacommunities revealed differing sets of favored metabolic pathways and life strategies. In one community, taxa with methanogenic metabolism were common, while a second community was dominated by taxa with carbohydrate and lipid-focused metabolism. Conclusion The identification of ubiquitous persistent co-occurring bacterial metacommunities in freshwater habitats could potentially facilitate microbial source tracking analysis of contamination issues in freshwater sources.
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| 4. |
- Dahl, Gordon B., et al.
(författare)
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Family Spillovers in Field of Study
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper estimates peer effects both from older to younger siblings and from parents to children in academic fields of study. Our setting is secondary school in Sweden, where admissions to oversubscribed fields is determined based on a student's GPA. Using an RD design, we find strong spillovers in field choices that depend on the gender mix of siblings and whether the field is gender conforming. There are also large intergenerational effects from fathers and mothers to sons, except in female-dominated fields, but little effect for daughters. These spillovers have long-term consequences for occupational segregation and wage gaps by gender.
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| 5. |
- Dahl, Gordon B., et al.
(författare)
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High School Majors and Future Earnings
- 2023
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Ingår i: American Economic Journal. - : American Economic Association. - 1945-7782 .- 1945-7790. ; 15:1, s. 351-382
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Tidskriftsartikel (refereegranskat)abstract
- We study how high school majors affect adult earnings using a regression discontinuity design. In Sweden students are admitted to majors in tenth grade based on their preference rankings and ninth grade GPA. We find engineering, natural science, and business majors yield higher earnings than social science and humanities, with major-specific returns also varying based on next-best alternatives. There is either a zero or a negative return to completing an academic program for students with a second-best nonacademic major. Most of the differences in adult earnings can be attributed to differences in occupation, and to a lesser extent, college major.
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| 6. |
- Dahl, Gordon B., et al.
(författare)
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Long-Run Returns to Field of Study in Secondary School
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper studies whether specialized academic fields of study in secondary school, which are common in many countries, affect earnings as an adult. Identification is challenging, because it requires not just quasi-random variation into fields of study, but also an accounting of individuals’ next-best alternatives. Our setting is Sweden, where at the end of ninth grade students rank fields of study and admissions to oversubscribed fields is determined based on a student’s GPA. We use a regression discontinuity design which allows for different labor market returns for each combination of preferred versus next-best choice, together with nationwide register data for school cohorts from 1977-1991 linked to their earnings as adults. Our analysis yields four main findings. First, Engineering, Natural Science, and Business yield higher earnings relative to most second-best choices, while Social Science and Humanities result in sizable drops, even relative to non-academic vocational programs. Second, the return to completing a field varies substantially as a function of a student’s next-best alternative. The magnitudes are often as large as estimates of the return to two years of additional education. Third, the pattern of returns for individuals with different first and second best choices is consistent with comparative advantage for many field choice combinations, while others exhibit either random sorting or comparative disadvantage. Fourth, most of the differences in adult earnings can be attributed to differences in college major and occupation. Taken together, these results highlight that the field choices students make at age 16, when they may have limited information about their skills and the labor market, have effects which last into adulthood.
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| 7. |
- D'Angiolo, M., et al.
(författare)
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A yeast living ancestor reveals the origin of genomic introgressions
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 587, s. 420-425
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Tidskriftsartikel (refereegranskat)abstract
- A yeast clonal descendant of an ancient hybridization event is identified and sheds light on the early evolution of the Saccharomyces cerevisiae Alpechin lineage and its abundant Saccharomyces paradoxus introgressions. Genome introgressions drive evolution across the animal(1), plant(2) and fungal(3) kingdoms. Introgressions initiate from archaic admixtures followed by repeated backcrossing to one parental species. However, how introgressions arise in reproductively isolated species, such as yeast(4), has remained unclear. Here we identify a clonal descendant of the ancestral yeast hybrid that founded the extant Saccharomyces cerevisiae Alpechin lineage(5), which carries abundant Saccharomyces paradoxus introgressions. We show that this clonal descendant, hereafter defined as a 'living ancestor', retained the ancestral genome structure of the first-generation hybrid with contiguous S. cerevisiae and S. paradoxus subgenomes. The ancestral first-generation hybrid underwent catastrophic genomic instability through more than a hundred mitotic recombination events, mainly manifesting as homozygous genome blocks generated by loss of heterozygosity. These homozygous sequence blocks rescue hybrid fertility by restoring meiotic recombination and are the direct origins of the introgressions present in the Alpechin lineage. We suggest a plausible route for introgression evolution through the reconstruction of extinct stages and propose that genome instability allows hybrids to overcome reproductive isolation and enables introgressions to emerge.
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| 8. |
- Hazer Rosberg, Derya Burcu, et al.
(författare)
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Gold and cobalt oxide nanoparticles modified poly‐propylene poly‐ethylene glycol membranes in poly (E‐caprolactone) conduits enhance nerve regeneration in the sciatic nerve of healthy rats
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 22:13
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Tidskriftsartikel (refereegranskat)abstract
- Reconstruction of nerve defects is a clinical challenge. Autologous nerve grafts as the gold standard treatment may result in an incomplete restoration of extremity function. Biosynthetic nerve conduits are studied widely, but still have limitations. Here, we reconstructed a 10 mm sciatic nerve defect in healthy rats and analyzed nerve regeneration in poly (ɛ‐caprolactone) (PCL) conduits longitudinally divided by gold (Au) and gold‐cobalt oxide (AuCoO) nanoparticles embedded in poly‐propylene poly‐ethylene glycol (PPEG) membranes (AuPPEG or AuCoOPPEG) and compared it with unmodified PPEG‐membrane and hollow PCL conduits. After 21 days, we detected significantly better axonal outgrowth, together with higher numbers of activated Schwann cells (ATF3‐labelled) and higher HSP27 expression, in reconstructed sciatic nerve and in corresponding dorsal root ganglia (DRG) in the AuPPEG and AuCoOPPEG groups; whereas the number of apoptotic Schwann cells (cleaved caspase 3‐labelled) was significantly lower. Furthermore, numbers of activated and apoptotic Schwann cells in the regenerative matrix correlated with axonal outgrowth, whereas HSP27 expression in the regenerative matrix and in DRGs did not show any correlation with axonal outgrowth. We conclude that gold and cobalt‐oxide nanoparticle modified membranes in conduits improve axonal outgrowth and increase the regenerative performance of conduits after nerve reconstruction.
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| 9. |
- Odelstad, Elias, et al.
(författare)
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Plasma Density and Magnetic Field Fluctuations in the Ion Gyro-Frequency Range Near the Diamagnetic Cavity of Comet 67P
- 2020
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Ingår i: Journal of Geophysical Research - Space Physics. - WASHINGTON DC USA : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 125:12
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of large-amplitude, quasi-harmonic density fluctuations with associated magnetic field oscillations in the region surrounding the diamagnetic cavity of comet 67P. Typical frequencies are similar to 0.1 Hz, corresponding to similar to 10 times the water and less than or similar to 0.5 times the proton gyro-frequencies, respectively. Magnetic field oscillations are not always clearly observed in association with these density fluctuations, but when they are, they consistently have wave vectors perpendicular to the background magnetic field, with the principal axis of polarization close to field-aligned and with a similar to 90 degrees phase shift with respect to the density fluctuations. The fluctuations are observed in association with asymmetric plasma density and magnetic field enhancements previously found in the region surrounding the diamagnetic cavity, occurring predominantly on their descending slopes. This is a new type of waves not previously observed at comets. They are likely ion Bernstein waves, and we propose that they are excited by unstable ring, ring-beam, or spherical shell distributions of cometary ions just outside the cavity boundary. These waves may play an important role in redistributing energy between different particle populations and reshape the plasma environment of the comet.
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| 10. |
- Rooth, Dan-Olof, 1967-, et al.
(författare)
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Intergenerational and Sibling Spillovers in High School Majors
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper estimates family spillovers in high school major choice in Sweden, where admission to oversubscribed majors is determined based on GPA. Using a regression discontinuity design, we find large sibling and intergenerational spillovers that depend on the gender mix of a dyad. Same-gender siblings copy one another, while younger brothers recoil from older sister's choices. Fathers and mothers influence sons, but not their daughters, except when a mother majors in the male-dominated program of Engineering. Back of the envelope calculations reveal these within family spillovers have sizable implications for the gender composition of majors.
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