The characteristic polymorphism of the paracentric secondary constriction region of chromosome 9 and its specific staining by a Giemsa banding technique allowed the unequivocal identification of the No. 9 in human male meiosis.
Summary. Pachytene quadrivalents are described in a male heterozygous for a balanced reciprocal translocation between the long arms of chromosomes 10 and 11. The break points of the translocation occur at 10q23 and 1 1q24. The main chromomere patterns ofthe bivalents correspond to the main G bands in mitosis and are sufficiently pronounced to allow the identification of bivalents 10 and 11 in normal spermatocytes.In the meiotic analysis of a male heterozygous for a reciprocal translocation between the long arms of chromosomes 10 and 11, the pachytene cells were of unusual interest in that the translocation and its break points could be identified in a surprising number. The observations provide what appear to be the first illustrations of a pachytene quadrivalent in a mammal, being remarkably similar to those observed many years ago in an 8;9 translocation in maize (McClintock, 1930). They also suggest that the chromomere patterns of pachytene bivalents correspond in general to the main bands produced in mitotic chromosomes by Giemsa banding techniques, and lead to the identification of bivalents 10 and 11 in the human pachytene map. Materials and MethodsThe meiotic preparations were made from testis material obtained by biopsy from W.A., the father of a mentally retarded child who has an unbalanced karyotype, 46,XX,der(l 1),rcp(10;1 1)(q23;q24). The clinical and chromosomal findings, and the genetic marker studies in this child and her family are to be described elsewhere (Ferguson-Smith, Ellis, and Newman, in preparation). Immediately after removal, part of the testis material was placed in Waymouth's TCM +10% calf serum containing heparin and minced with scissors (Hungerford, 1971 were made and stained in 2% aceto-orcein for 3 minutes. Meiotic cells were examined and photographed using phase-contrast objectives. Mitotic preparations were made from lymphocyte cultures and were stained by the trypsin-Leishman technique (Seabright, 1971). Part of the testis material was fixed immediately and sectioned for pathological examination. ResultsHistological examination of sections of the testis material showed complete, active spermatogenesis without abnormality in all tubules. In particular, there was no sign of maturation arrest. Similarly, the meiotic preparations showed a normal proportion of cell types in metaphase, of which 10% were spermatogonial, 48% were in diakinesis, and 42% were in second meiotic metaphase. The translocation chromosomes could not be identified with certainty in any spermatogonial or second meiotic metaphase.Diakinesis. The presence of a translocation was confirmed in 44 cells in diakinesis all of which showed a quadrivalent. In 41 cells, there were 22 chromosomal elements including the sex bivalent so that the karyotype could be designated MI, 22,XY,IV(10;11). In three cells the karyotype was MI, 23,X,Y,IV(10;11), this being a normal frequency of cells in which the X and Y are separate.In 64% of cells the quadrivalent appeared as a "ring' (Fig. la) and in the remainder as a 'chain'
Cytogenetic study of 17 cases of chronic myeloid leukaemia has shown that the Philadelphia chromosome is a variable entity, differing in size and banding pattern between individuals.
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