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
Filter
  • 1970-1974  (3)
Material
Years
Year
  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Newts with chromosomal mutations have been isolated in female progeny of irradiated males. Detection and analysis of the mutations are based on the study of lampbrush chromosomes of the adult female oocytes. Selection of the mutants, then, concerns viable individuals only, which are apt to give rise to stem lines. The seven mutants have been separated into two groups: simple mutations and complex ones. The first group includes four mutants, three with a reciprocal translocation and one with a pericentric inversion. The translocation carriers have reproduced, but, in the three cases, mortality was high during embryogenesis. The genetic unbalance proves to be the cause, so that survivors correspond to parental karyotypes only. On the contrary, the female with the pericentric inversion, produced offspring, whose primary anomalies, as well as the secondary unbalanced ones (duplication-deficiency) are viable. Meiotic figures allow estimates of the frequency and importance of the unbalance. The second group includes three mutants, the first with two inversions and a reciprocal translocation, the second has two translocations involving five bivalents, the third carries only one chain of translocation, including five bivalents. Complex anomalies are frequent and appear to be viable, as long as they are balanced. One of the mutants gave rise to polyploid off-spring. Three mutations involved the sex bivalent. Suitability of lampbrush chromosomes as a tool of analysis of rearrangements is discussed. Translocations are systematically detected and very small chromosomal rearrangements can be observed.
    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 X-rays have been used to induce heritable changes in the specific morphology of the lampbrush chromosomes in the newt Pleurodeles waltlii. The karyotype organization of female progeny of irradiated males was studied. Nine out of ten females were found to have chromosomal aberrations. In one of the nine, one of the breaks occurred at the sphere organizer, the sphere being part of the striking morphological features of chromosome IV. On irradiation the normal sphere organizer had been broken into two fragments each of which, when recombined with other chromosome breaks, still forms a sphere. The relationship of these observations to genome redundancy is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electron-probe X-ray microanalysis showed that significant amounts of silicon are accumulated in the entire epidermal system of the rice internode except in the stomatal apparatuses. Thus, there is a lack of specific sites for Si deposition from levels just above the base to the tip of the rice internode. In the intercalary meristem region, 1 cm above the base of the internode, point-count data indicate more Si accumulation in the dumb-bell shaped silica cells than in the long epidermal cells. Above this region, Si is accumulated essentially in a uniform pattern in all epidermal cells. Such a pattern for Si accumulation in rice internodes markedly contrasts with that for Avena internodes and may explain, in part, why rice plants have a higher percentage Si (dry weight basis) in their shoots. The adaptive significance of this silicification pattern in rice is discussed.
    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...