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Chromosome studies. II. Synapsis in the Tettigidae, with special reference to the presynapsis split
Author(s) -
Robertson W. R. B.
Publication year - 1931
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1050510103
Subject(s) - tetrad , synapsis , prophase , biology , telophase , cell division , homologous chromosome , elongation , spermatocyte , genetics , trichoplusia , nucleus , bivalent (engine) , pairing , meiosis , chromosome , microbiology and biotechnology , botany , cell , physics , gene , metallurgy , superconductivity , organic chemistry , noctuidae , metal , materials science , chemistry , larva , ultimate tensile strength , quantum mechanics
Homologous chromosomes entering parasynapsis are already split. This split evidently originates in each chromosome in the resting period prior to the last spermatogonial division. In the prophase of this division the daughter chromonemata in each halfchromosome were probably incompletely separated, but the succeeding telophase effects the completion of their separation. These processes are accompanied and suceeded by an elongation, straightening, and general paralleling of the split threads and by an elongation of the cell and its nuclear space. Parasynapsis begins with intimate approximation of the daughter threads in each homologue and is continued by approximation of the homologues at the usual [bouquet] and [zygotene] periods. There results the [diplotene] thread, which therefore consists of four completely distinct strands, but which exhibits a [two‐strand] appearance due to parasynapsis between daughter chromonemata being further advanced than that between homologues. The pairing process begins at the distal ends and proceeds proximally. With parasynapsis complete, the nucleus enters the [diffuse] stage On emergence, disjunction is seen to have progressed from the distal ends to near the proximal ends in each pair and the [tetrads] have taken form. In the prephase that follows each strand in a tetrad may [crimp] independently, and with the condensation and matrix (?) formation that accompany it there results the spermatocyte ‘tetrad.’