ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-2242
    Keywords: Androgenesis ; Gynogenesis ; Tilapia Gene bank ; Chromosome manipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Androgenesis is a potentially valuable technique for recovering fish from gene banks composed of cryopreserved sperm, developing inbred lines, and analyzing patterns of inheritance. The procedure for producing diploid organisms whose nuclear DNA is wholly of paternal origin is dependent on: (1) the denucleation of “host” eggs, and (2) the inhibition of the first mitotic division in order to double the haploid sperm chromosome complement following fertilization of host eggs. Denucleation of tilapia (Oreochromis niloticus L.) eggs was carried out using UV irradiation. Treatment durations of 5–8 min (total dose of 450–720 J/m2) produced acceptable yields of viable denucleated eggs [22.9±1.6% (±SE) of controls] as estimated by the survival of haploid androgenetic tilapia to 48 h post-fertilization. Successful mitotic inhibition was accomplished using a heat-shock of 42.5 °C for 3–4 min, applied at 2.5-min intervals from 22.5 to 30 min post-fertilization (mpf). The mean survival of androgenetic diploid fish to yolk-sac absorption for treatment groups varied from 0.4% to 5.3%, relative to the controls. Differences in the suceptibility of eggs from different females to UV irradiation were a significant factor in the overall yield of androgenetic diploids. Paternal effects did not significantly influence the androgenetic yield, suggesting that individual males would not be selected against. For comparative purposes mitotic gynogenetic “mitogyne” diploids were produced from UV-irradiated sperm. Mean survival to yolk-sac absorption varied from 0.5% to 10.64%, relative to controls. Similar optima for androgenetic and gynogenetic induction were found in the period 25–27.5 mpf (minutes post-fertilization). Induction treatments would appear to be operating on the same developmental events in both these techniques, and the results suggest that the UV irradiations used do relatively little damage to the eggs beyond nuclear inactivation. The results indicate that the production of androgenetic O. niloticus is possible on a consistent basis and that the application of this technique may be useful in quantitative and conservation genetics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-2242
    Keywords: Sex determination ; Oreochromis niloticus ; Gynogenesis ; Sex reversal ; Triploidy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Established techniques of genetic manipulation were used to elucidate sex-determining mechanisms in the commercially important tilapia, Oreochromis niloticus. Analysis of sex ratios from single-pair matings of normal broodstock showed these to be heterogeneous, with an asymmetrical frequency distribution. Data were homogeneous, with the exclusion of a number of broods with sex ratios not significantly different from 3∶1 (male: female), and further progeny testing revealed atypical female heterogamety in the parents of these broods. Analysis of sex ratios from complete diallele-type crosses using five males and five females demonstrated no association between male parent, female parent and progeny sex ratio. Sex ratios of gynogens (0∶1) and triploids (1∶1), and from progeny testing of sex-reversed males (0∶1) and sex-reversed females (3∶1), provide evidence for female homogamety in this species. Progeny testing of male gynogens derived from sex-reversed females demonstrated recombination between the centromere and the sex-determining locus (68.9%). Novel YY “supermales” were shown to be viable and produced all-male offspring. It was concluded that this species exhibits monofactorial, genotypic sex determination with male heterogamety. However, rare autosomal or environmental sex-modifying factors may account for occasional deviations from expected sex ratios.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2242
    Keywords: Sex determination ; Oreochromis aureus ; Gynogenesis ; Sex reversal ; Hybridisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 1∶1, 3∶5 and 1∶3 (male∶female). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (1∶3) and most sex-reversed females (1∶0) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW “superfemale”, which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: High temperature (36° C) treatment during sexual differentiation caused significant changes in sex ratio in YY male Nile tilapia Oreochromis niloticus fry (64.5% males compared to 100.0% males at 28° C), while dietary treatment with a chemical aromatase inhibitor (AI: Fadrozole™ CGS16949A) during this period suppressed the high temperature feminization (98.9% males). This implies that cytochrome P450 aromatase is mechanistically associated with temperature-dependent sex determination (TSD) in this species. XY male fry did not show significant sex reversal at 36° C. In XX female fry, high temperature treatment resulted in significant masculinization (62.5% males compared with 21.9% males at 28° C), while treatment with AI at either temperature resulted in very high proportions of males (100.0% males at 36° C; 99.0% males at 28° C). These results confirm the importance of aromatase in sexual differentiation in the Nile tilapia below the TSD threshold and suggest that it also plays a role in TSD, at least in the YY genotype.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1040-452X
    Keywords: Transgene inheritance ; Rainbow trout ; Founder generation transgenics ; DNA ; MTrGH ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: There have been very few studies of the inheritance of introduced genes (transgenes) in fish. We have followed the inheritance of the mammalian fusion gene MTrGH from founder generation transgenics (originating from eggs microinjected with the MTrGH DNA) to offspring in crosses with control fish.Initial screening of the founder generation transgenics was by analysing DNA from blood samples. Only three out of six fish which carried the novel gene in blood DNA transmitted it to their offspring, despite the presence of the gene in DNA extracted from the sperm of all four male fish in this group. The frequency of transgenics in the progeny groups from the three fish which transmitted the gene varied widely: in one of these groups more than one type of MTrGH restriction pattern was found. These results suggest widespread mosaicism in founder generation transgenics.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A range of phenotypic characters were measured and their mean and coefficient of variation (CV) calculated in meiotic and mitotic gynogenetic individuals and normal diploids produced from the same full-sib family of Oreochromis niloticus (L.). The traits studied in all three groups were weight, length, various fin ray and scale counts, gonadosomatic index (GSI) and reproductive response. The study revealed two main trends in the majority of the traits studied in the gynogenetic fish: a decrease in the mean of each trait in the ranked order normal diploid 〉 meiotic gynogenetic 〉 mitotic gynogenetic, and an expansion of its phenotypic variation (CV) in the order normal diploid 〈 meiotic gynogenetic 〈 mitotic gynogenetic. This could be related to the levels of genetic homozygosity and a possible reduction in developmental homeostasis in the gynogenetics. The utility and potential of gynogenetic individuals in research and the use of the technique in the improvement of fish strains for aquaculture are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Spontaneous diploidization of the maternal chromosome set (SDM) in Oreochromis niloticus is described here for the first time. The SDM phenomenon was observed in progeny of only one XY neofemale out of 11 such neofemales from which eggs had been fertilized with UV-irradiated sperm: this treatment produced only the expected haploid embryos from the other females. SDM progeny were produced from three different batches of eggs from this female. No significant differences in survival at different stages of embryonic development were observed between the SDM and the diploid control group. The maternal inheritance of SDM progeny was verified using multilocus DNA fingerprinting. Only diploid karyotypes were observed in these fish and diploid control groups. In both the SDM and control groups, sex ratios were significantly skewed towards males (93.3% and 65.0% males respectively). The actual mechanism of SDM in eggs from this particular female remains unknown.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The karyotypes of both Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell) are shown to consist of 22 pairs of chromosomes (2n = 44). In O. mortimeri, the karyotype is composed of 9 sm/st and 13 t chromosomes. In the case of S. melanotheron, the karyotype is composed of 15 sm/st, 2 m and 5 t chromosomes. The karyotypes of these species are therefore similar to those of the majority of other tilapia species, with that of S. melanotheron being considerably different from that previously reported for this species.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The karyotype of the Atlantic halibut, Hippoglossus hippoglossus, (Linnaeus, 1758) consists of 24 pairs of chromosomes (2n= 48) all of which are subtelocentric or acrocentric. The number and morphology of the chromosomes of the Atlantic halibut is therefore similar to most other pleuronectid fish studied.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...