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
    Synaptonemal complex analysis of mouse chromosomal rearrangements (1981)
    Springer
    Chromosoma 81 (1981), S. 519-535 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Surface spread spermatocytes of mice heterozygous for a tandem duplication show nuclei in late zygotene-early pachytene in which the heteromorphic synaptonemal complex (SC) contains a lateral element that is buckled out into an unpaired loop as a consequence of the added length of the duplication (estimated in another study to be 21.7%, with breakpoints at 0.50 and 0.72 of the length of the chromosome). The ends of the buckle, marking the interstitial termini of synapsis proceeding from opposite directions, vary over a wide range of positions, but within limits: the proximal end of the loop does not exceed the distal end of the duplication segment, while the distal end of the loop does not lie closer to the kinetochore than the proximal end of the segment. Thus, synapsis (SC formation) at zygotene is restricted to homologous regions (exclusive homosynapsis). — In the last half of pachytene, no buckles are found, only simple SCs with lateral elements of equal length, as a consequence of synaptic adjustment. Intermediate stages of adjustment are found throughout the first half of pachytene. Shortly after homosynapsis is complete, synaptic adjustment begins: the ends of the duplication loop separate (desynapsis of homosynapsed regions); the long axis shortens with respect to the short axis in both the unpaired loop and in the SC portions; asymmetrical twists take up inequalities; the loop is reduced to from 1 to 3 asymmetrical twists; the axes (lateral elements) equalize as the long axis shortens; and a simple SC is formed, indistinguishable from others in the complement, in which the region of the duplication and those adjacent to it have heterosynapsed, while the distal regions of the SC are presumably still homosynapsed. Synaptic adjustment evidently involves two sequential events: localized instability of the homosynapsed condition, leading to desynapsis, then restoration of the SC by heterosynapsis. Adjustment therefore represents the loss of strict homosynapsis. It is concluded that the asymmetry produced by the duplication loop constitutes an instability that triggers synaptic adjustment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285847
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Synaptonemal complex analysis of mouse chromosomal rearrangements (1981)
    Springer
    Chromosoma 81 (1981), S. 507-518 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Electron microscopy of surface-spread spermatocytes from mice heterozygous for a tandem duplication shows the heteromorphic synaptonemal complex (SC) to comprise two lateral elements of unequal length, the longer of which is buckled out in a characteristic loop, representing the unsynapsed portion of the duplication. The loop is a regular feature of late zygotene-early pachytene nuclei; it is longest at these early stages, but, through equalization of the two axes as a consequence of synaptic adjustment, it is replaced by a normal appearing SC at late pachytene. Because equalization, as indicated by a decrease in the percent difference between axes, may begin shortly after completion of synapsis, estimates of duplication segment length are restricted to a sample selected for least adjustment. — Although the mean position of the loop is constant at various pachytene substages, individual positions vary widely from cell to cell, consistent with the behavior expected of a duplication, but not of a deletion or an inversion. The length of the segment that is duplicated is estimated to be 22% of the normal chromosome, the midpoint of the segment is mapped at 0.61 of the chromosome distal to the kinetochore, and the ends of the segment are mapped at 0.50 to 0.72. Measurements of G-banded mitotic chromosomes give comparable values: duplication length, 24%; midpoint, 0.60, and segment ends, 0.48 and 0.71. This agreement constitutes further validation of the SC/spreading method for detecting and analyzing chromosomal rearrangements at pachytene and substantiates the fidelity with which the axes and SCs represent the behavior of chromosomes in synapsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285846
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Synaptonemal complex analysis of mouse chromosomal rearrangements (1981)
    Springer
    Chromosoma 83 (1981), S. 419-429 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Synaptonemal complex (SC) analysis by electron microscopy of spermatocytes in surface microspreads was carried out in mice heterozygous for two paracentric inversions: either In(1)1RK or In(2)5Rk. Characteristic SC inversion loops are formed at synapsis in bivalents carrying the rearrangements. Although all loops were observed to be eliminated by late pachytene through synaptic adjustment, every spermatocyte at early pachytene contained a fully synapsed loop. Cells in the earliest stage of pachytene contained the longest loops and thus had undergone minimal adjustment. The SC estimates of inversion lengths and breakpoint positions in such cells corresponded well with those from mitotic chromosome banding and could be correlated with genetic maps of chromosomes # 1 and # 2, thus demonstrating the basis for the mapping of pachytene chromosomes. The regularity of loop formation and reproducibility of the SC analysis are reflected in the constant relative positions of the estimated breakpoints. The method is sensitive enough to reflect small, real, interstitial length differences between meiotic and mitotic chromosomes. The results demonstrate the feasibility and precision of detection and quantitative characterization of inversions at early meiotic prophase by SC analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327363
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Synaptonemal complex analysis of mouse chromosomal rearrangements (1982)
    Springer
    Chromosoma 84 (1982), S. 457-474 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two paracentric inversions in the mouse, In(1)1 Rk and In(2)5 Rk, have been studied in surface microspreads of spermatocytes from heterozygotes. At zytogene, synaptic initiation occurs independently in three regions: within the inversion, and without, on either side. Synaptonemal complex (SC) formation is restricted to homologous regions, resulting in inversion loops in all early pachytene spermatocytes. An adjusting phase then occurs during pachytene in which the inversion loop is reduced by desynapsis of homologously synapsed SC, followed immediately by non-homologous synapsis with the alternate pairing partner, progressing from the ends toward the middle. Adjustment occurs during the first half of pachytene, but is not closely synchronized with sub-stage. It is complete by late pachytene, the loop having been eliminated in all cases and replaced by “straight” SCs in which the inverted region is heterosynapsed. Synapsis in the adjustment phase is evidently permitted only after the homosynaptic phase, and is indifferent to homology. It may lead to heterosynapsis, as in the inversion region, or to synapsis of homologous regions not synapsed at zytogene. The anaphase bridge frequency, a measure of crossing over within the inversion, is about 34% for both inversions studied, indicating that such crossovers do not block adjustment, that crossing over probably occurs before or during the adjustment period, and that there is some crossover suppression. The last could be the consequence of blocking by desynapsis/heterosynapsis. Synaptic adjustment appears to be a general phenomenon that occurs to varying extents in different forms. A hypothetical scheme for two phases of synapsis is proposed: at zytogene, a basic propensity for indifferent SC formation is limited by a restricting condition to synapsis between homologous regions. Subsequently, the restriction is lifted, whereupon synaptic instability is resolved by desynapsis, followed by resynapsis that is indifferent to homology, but that results in a topologically more stable structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292848
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Association of foreign DNA sequence with male sterility and translocation in a line of transgenic mice (1989)
    Springer
    Somatic cell and molecular genetics 15 (1989), S. 569-578 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have analyzed a line of transgenic mice derived from injection of a cloned human interferon cDNA. This line manifests total male sterility of males carrying the human sequence, while male littermates not harboring the foreign DNA are fertile. All females are fertile. Karyotypes of transgenic animals show 2∶12 translocation. The microinjected sequence maps to one of the translocation chromosomes composed of a large portion of chromosome 12 to which has been translocated a segment of chromosome 2. Analysis of the sterile males reveals significant abnormalities of spermatogenesis and faulty chromosome synapsis that involves the translocation chromosomes. These findings show that transfer of foreign DNA into mouse embryos may lead to chromatin breakage and infertility of transgenic animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01534918
    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...