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During embryonic development in mammals, most of the methylated cytosines in the paternal genome are converted to 5-hydroxymethyldeoxycytidine (hmC), as part of DNA methylation reprogramming. Recent data also suggest tissue-specific functional roles of hmC, perhaps as an epigenetic mark. However, limited data are available on the levels and tissue distribution in zebrafish. In this study, we used high-performance liquid chromatography mass spectrometry to quantify hmC and 5-methyldeoxycytidine (mC) in zebrafish during development and in different tissues of the adult fish. Low levels of mC were found at 0.5 hours postfertilization (hpf) (1-2 cell stage) (1.9%), and increased to 8.4% by 96 hpf, with similar levels observed in different adult tissues. No hmC was detected up to 12 hpf, but levels increased during development from 24 up to 96 hpf (0.23%). In tissues, the highest levels of hmC were found in the brain (0.49%), intermediate levels in muscle (0.13%), liver (0.08%), and intestine (0.06%) and low levels in testis (0.01%), with an inverse correlation between hmC and mC. Our results indicate similar tissue distribution and levels of hmC between zebrafish and mammals, but distinct differences during embryonic development. Although more research is needed, these results support the use of zebrafish as an alternative model in the elucidation of tissue-specific functions of hmC.

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Sammendrag Dette kapitlet retter et kritisk, men konstruktivt blikk på naturfag, og foretar en gjennomgang av naturfag og naturfagdidaktikk innen forskning og i praksis. Kapitlet starter med å beskrive og diskutere naturfagets kjennetegn, verdi og relevans. Her kastes det lys på hva som er fagets og naturvitenskapens egenart, og hvorfor og hvordan naturfag er verdifullt og relevant. Videre beskrives og diskuteres naturfag på tre nivåer eller fra tre perspektiver: 1) på system-og politikknivå (antall timer til naturfag, realfagssatsing og laereplan), 2) på laerernivå (laereres kompetanse, etterutdanning og undervisning) og 3) på elevnivå (elevers kompetanse og motivasjon). Innen hvert av disse nivåene beskrives først tilstanden og hvordan gunstige betingelser ville ha vaert (f.eks. hva kjennetegner god undervisning), og deretter diskuteres utfordringer og muligheter. Kapitlet avsluttes med en oppsummering og diskusjon av veien videre.

The article examines gender and recruitment for mathematics and science through a close reading of four women’s stories about choosing a mathematics and science education, retrieved from a more comprehensive study of educational choice. Personal interest for the subject is an established understanding of what influence the educational choice. Strategies and campaigns for recruiting women for mathematics and science have thus been geared to awaken precisely women’s interest as women In this article, we move away from an understanding of gender as a background variable to explain "interest in mathematics and science", and instead show how educational choice can be understood as socio-material practices. In the interaction between human and material actors there is also bodily experiences, something which gives gender active significance (agency). Thus, the article contributes to an extended understanding of the components that are included in educational choice and how these components relate to one another, which in turn provides new opportunities for understanding how educational choices can beaffected through material experiences and practices.