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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 55 (1933), S. 265-311 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: X-rays produce fragmentations of the chromosome commonly in the region of fiber attachment.Fiberless fragments become attached to other chromosomes or those portions of them that retain fiber attachments. Thus, chromosomes homologous to parts of two other chromosomes are produced and at synapsis multiples are formed. Such multiples are chains or closed-circles depending upon whether a single or a reciprocal translocation respectively has occurred. Sometimes entire chromosomes unite to form a multiple. In general, the multiples divide so that the segregation of homologous elements is complete. However, sometimes the separation of homologous portions is impossible and, then, gametes which contain sectional-duplications, or sectional-deficiencies, or both, are produced. Any two or more chromosomes may be involved in multiple formation although the larger elements are more frequently implicated.Translocations may occur between homologues resulting in an unequal division of chromatin.The locus of fiber attachment (acromite) is an integral part of a chromosome and its loss to one homologue causes non-disjunction or other inequalities in the distribution of the chromatin.Supernumerary chromosomes are frequently present in the spermatocytes.Homologues unaccountably sometimes fail to synapse in the descendants of irradiated cells.There is a striking similarity between natural and induced chromosomal aberrations as well as a correlation between the distribution of radioactive minerals and naturally occurring aberrations.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 71 (1942), S. 1-33 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 47 (1929), S. 1-36 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The first spermatocytes of Circotettix verruculatus have eleven chromosomes. Five of these are regularly atelomitic and three are telomitic. The other three are variable and may have both diads telomitic, both atelomitic, or one diad telomitic while the other is atelomitic. The locus of fiber attachment and, consequently, the form of the chromosome are constant for the individual. The point of fiber insertion is known to be inherited according to mendelian principles, and is, therefore, a measure of the frequencies of the telomitic and atelomitic diads in a group of individuals.Samples of five geographically different populations were studied with respect to the proportion of atelomitic to telomitic diads in the three variable tetrads. The proportion for each of the three chromosomes was compared with that for the corresponding tetrads from the other localities. The data were subjected to statistical analysis, and significant differences between some of the groups were found in the proportion of atelomitic to telomitic diads in corresponding chromosomes.A possible correlation between these cytological differences among the various localities and the formation of geographical races or subspecies are discussed. An inversion of the portion of a chromosome, which causes an apparent, although not a real, change in the locus of fiber attachment, is suggested as the origin of atelomitic chromosomes. The effect which heteromorphism of synaptic mates may have on crossing-over is considered.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 69 (1941), S. 317-327 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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