Library

X
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
    Electronic Resource
    Electronic Resource
    The W-chromosome of the budgerigar, Melopsittacus undulatus (1963)
    Springer
    Chromosoma 14 (1963), S. 459-467 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The chromosome complement of male and female budgerigars (Melopsittacus undulatus) was studied in primary kidney cell cultures. van Brink's description of the male complement was confirmed. The 26 largest chromosomes can unequivocally be placed in 13 pairs. In the female the fifth largest chromosome is single ; it is the Z-chromosome, again confirming van Brink. In addition in all females and none of the males a previously undescribed extra chromosome was found, in size between pairs 9 and 10 with arm ratio 1∶1.5 and negatively heteropycnotic at metaphase. It is identified as the W-chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321467
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Chromosome size and DNA content of species of anemone L. and related genera (Ranunculaceae) (1966)
    Springer
    Chromosoma 20 (1966), S. 54-74 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Relative amounts of DNA were determined by Feulgen cytophotometry in 22 diploid species of Ranunculaceae (n=7, 8, 9) representing six genera, and exhibiting large differences in chromosome size, but no marked differences in karyotype pattern. Chemical determination of absolute amounts of DNA for six of these species, allowed conversion of all the photometric data into absolute units of DNA. The mean DNA content per nucleus varied from.13×10−11gm in Aquilegia to 5.25×10−11gm in species of Anemone in the section Homalocarpus. The DNA values obtained appeared to be “quantized”, and data for the majority of species fitted a non-geometrical series with the observed relative terms: 1—8—12—16—20—24—40. The magnitude of these variations in DNA content, the preservation of the karyotype and the tendency towards a simple numerical progression in DNA values, lead us to prefer an interpretation of the evolution of DNA content in terms of differential polynemy to one postulating changes in size of genetic units in an unchanging number of strands per chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331898
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The B-chromosomes of Neopodismopsis abdominalis (Orthoptera, Acrididae) (1975)
    Springer
    Chromosoma 52 (1975), S. 137-148 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract As an extension of an earlier study, the behaviour of two kinds of supernumerary chromosomes has been re-examined in populations of Neopodismopsis abdominalis (Acrididae) from Ontario. One of these is minute and metacentric (BS); the other is large and heterochromatic (BL). The BS has a 40% probability of undergoing precocious separation when present as a univalent. This separation may lead to restitution and subsequently to macrospermatid formation. The frequency of macrospermatids was a power function of the number of precocious BS elements per cell and approached 20% in 4BS-individuals. Individuals with high numbers of BS occur in slight excess of Poisson expectation possibly reflecting a mechanism which compensates for the detrimental effects of the BS. The BL, by contrast, does not undergo precocious division and neither micro- nor macro-spermatids ascribable to the BL were seen. Non-disjunction of B-chromosomes occurred very rarely and was seen in only three BS individuals out of 141 examined and in only two BL individuals out of 33. Moreover it was equally frequent in caeca and gonad and did not result in a net loss or a net gain of B-chromosomes in the germ line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326263
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A cytological study of natural hybrids between Prosimulium multidentatum and P. magnum (1981)
    Springer
    Chromosoma 82 (1981), S. 673-691 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In a limited area of sympatry in New York State, hybridization occurs between Prosimulium multidentatum (Twinn) and “forms” 2 and 3 of P. magnum Dyar and Shannon. Salivary gland chromosomes of the interspecific hybrids are the composite of those of the parental species with respect to fixed inversion differences, sex chromosomes and chromocenter attachment of centromeres. Backcross hybrids with P. multidentatum occur in the same area. The preferred direction of cross (P. multidentatum ♀ x P. magnum ♂) is rationalized by the earlier emergence of P. multidentatum, and the earlier emergence of males and greater longevity of females of both species. Chromosome pairing, both in F1 and backcross, is loose in hybrid segments and tight in species homozygous parts. Likewise chiasma frequency is low in hybrid as compared to parentally homozygous chromosomes. In the face of locally recurrent hybridization species integrity is maintained by meiotic irregularities in the hybrids and especially by disturbances in the sex chromosome balance of backcross hybrids, the sex chromosomes of P. multidentatum and P. magnum being non-homologous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285775
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...