Library

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: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using colchicine, two methods have been successfully applied for the induction of tetraploid meiocytes at premeiotic mitosis in the near achiasmate diploid hybrid cultivar “Black Beauty” of Lilium. The experiments were aimed at understanding whether the achiasmate condition is attributable to insufficient homology for effective pairing or to some genie defect in order to interpret the data obtained from molecular studies. Cytological observations demonstrate a strong correlation between the induction of tetraploidy and subsequent chiasma formation. The chiasma frequency per cell in untreated diploid control meiocytes ranged from 0 to 8 (mean 2.25), while in colchicine treated undoubled cells sampled 14±2 days after the start of treatment it ranged from 0 to 2 (mean 0.148). By comparison, the chiasma frequency per cell in colchicine-doubled tetraploid cells ranged from 29 to 51 (mean 42.24), such cells showing complete or near complete bivalent pairing. These results, similar to those reported previously for other higher plant species, demonstrate that the achiasmatic condition in “Black Beauty” is not due to a genie defect. The methods developed have made possible hitherto inaccessible biochemical analyses of meiocytes that had been treated with colchicine or other chemicals at premeiotic stages.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Achiasmate meiocytes of Lilium cv. Black Beauty do not undergo DNA nicking at pachytene, nor do they acquire the high level of R-protein during zygotene-pachytene that is characteristic of chiasmate types. Induction of tetraploidy in such meiocytes with its accompanying increase in chiasma frequency results in a pachytene nicking pattern that is indistinguishable from what occurs in chiasmate plants. R-protein also increases to a level that on a per diploid genome basis is at least as high, and probably higher, than the level of chiasmate diploids. The absence of nicking in the achiasmate diploid is not due to a lack of appropriate enzyme activity but seems to result from the fact that unpaired or ineffectively paired chromosome regions are not accessible to the enzyme. The regulation of R-protein level by homologous pairing is examined but remains poorly understood.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 72 (1979), S. 175-189 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Chromosome pairing and chiasma frequency were studied in meiocytes at diakinesis of Lilium speciosum cv. “Rosemede” fixed up to 21 days after the start of either continuous or 3 day pulse colchicine treatment. The two treatments gave similar results. In pulse treated pollen mother cells (PMCs) the mean chiasma frequency per cell fell from 26.4 in controls to 8.5 after fourteen days while the mean number of univalents per cell increased from 0.05 to 17.58. There was a negative correlation between mean chiasma frequency per bivalent and per PMC in colchicine treated buds; univalents were preferentially induced in bivalents with one chiasma, and preferentially excluded in bivalents with 4 chiasmata. Some chiasmata were redistributed to surviving bivalents despite the concurrent reduction in chiasma frequency per meiocyte. — Colchicine sensitivity began in premeiotic interphase and extended to mid or late zygotene in PMCs; ongoing synapsis was unaffected. However, susceptibility to univalency was asynchronous between bivalents occurring at zygotene in short chromosomes but at late premeiotic interphase in the longest chromosomes. The number of chiasmata per bivalent could be altered by colchicine without inducing univalents, but the ultimate effect was to reduce the number of chiasmata per bivalent (or per chromosome arm) directly to zero. The major factors determining the order and extent of reduced pairing and chiasma number were total chromosome length and arm length. Pairing and chiasma formation in embryo sac mother cells were less sensitive to colchicine than in PMCs, but their behavior was otherwise similar.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 27 (1971), S. 1096-1097 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Résumé La présence d'un phéromone d'attraction sexuelle dans une espèce de diptère,Bradysia tritici, avec des considérations sur l'importance de cette substance dans la formation des espèces est décrit.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...