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  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In order to clarify the relationship between meiotic pairing and recombination, and electron microscopic (EM) study of synaptonemal complexes (SC) and an analysis of chiasma frequency and distribution were made in male mice singly and doubly heterozygous for Robertsonian [Rb(16.17)7Bnr] and reciprocal [T(16:17)43H] translocations and also in tertiary trisomics for the proximal region of chromosome 17. In all these genotypes an extensive zone of asynapsis/desynapsis around the breakpoints was revealed. At the same time a high frequency of non-homologous pairing was observed in precentromeric regions of acrocentric chromosomes. The presence in the proximal region of chromosome 17 of the t haplotype did not affect the synaptic behaviour of this region. Chiasma frequency in the proximal region of chromosome 17 in the T(16:17)43H heterozygotes and trisomics was increased when compared with that in Robertsonian heterozygotes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We determined the sequence of Tu80, one of the molecular clones derived from microdissected fragments of Chromosome (Chr) 17. The sequence data demonstrated that Tu80 contains an open reading frame (ORF) of 204 bp. Two sequences within the ORF, one homologous to the LINE1 element and the other to the first intron of the C ε gene of mouse immunoglobulin, were observed. A separate sequence, homologous to Tu80, designated as NOV1, was isolated from a genomic library of mouse Chr 17. NOV1 was found to contain an inserted B2 repeat, making it structurally different from Tu80. The sequences of Tu80 and NOV1 were compared with those of LINE1 and the first intron of the C ε gene. The results suggest that the ancestor of the Tu80-like sequence might have arisen through recombination between a LINE1 element and the C ε gene. It is concluded that Tu80 and NOV1 might have resulted from duplication of an ancestral sequence followed by divergence. The comparative analysis also demonstrated a high degree of conservation of the LINE1-like sequence in Tu80 and NOV1. Based on the structure of human, rat, rabbit, and mouse LINE1 fragments, as well as those of NOV1 and Tu80, a phylogenetic tree was constructed. The available data tend to support the assumption that the ancestor for the Tu80-like sequence might have arisen not later than 27–33 million years ago.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 11 (1990), S. 263-269 
    ISSN: 0192-253X
    Keywords: Penetrance ; reciprocal effects ; suppressor genes ; developmental cycle in mammals ; initialization ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The phenomenon of gametic imprinting in mammals has raised developmentally relevant questions concerning the manifestation and inheritance of genes with variable penetrance. The dominant fused (Fu) gene located on chromosome 17 is one of the few good cases demonstrating the phenomenon in mice. The Fu mutation has a maternal effect.We have previously shown that the † 12 haplotype significantly lowers the penetrance of Fuin ♀ ♀ Fu/†12 offspring. Results of recipiocal matings of the heterozygotes for Fu indicated that the Fu of maternal origin has a lowered level of penetrance. The dominant suppressors locotad outside chromosome 17, in contrast to †12 residing in it, had stronger effects on the manifestation of Fu, decreasing its penetrance to 8-17%. Experimental evidence is presented that the pathway via which Fu passes to the zygote nucleus during gametogenesis through successive generations has a marked effect on its penetrance. Based on this evidence, patterns of genetic imprinting are described. A survey of genetic imprinting allowed us to distinguish two developmental phases, gametic and zygotic. The hypothesis for the gametic phase of the development of multicellular organisms suggests that it proceeds from initialization, a process thought to ensure the freeing of chromosomes from redundant epigenetic information and their preparation for the consecutive developmental cycle.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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