In meiotic cells, from leptotene to diakinesis stages, the X chromosome shows positive heteropycnosis
, and is usually located outside the autosomal chromatin mass (Fig.
White's (1940a) first paper dealing with orthopteran sex chromosomes was a lengthy discussion about their heteropycnosis in different stages of mitosis and meiosis.
Today we know that such differential heteropycnosis is due to facultative heterochromatinization, due to epigenetic changes of the X chromosome chromatin.
Negative heteropycnosis, transcription activities and compartmentation during spermatogonial stages.
The heteropycnosis of sex-chromosomes and its interpretation in terms of spiral structure.
scorpioides exhibits positive heteropycnosis
in germinal cells of males.
of Sex Chromosomes and its Interpretation in Terms of Spiral Structure.
The cells with nine chromosomal elements included the X chromosome (n = 9 = 8 + X) that was always easily recognized by its large size and positive heteropycnosis
Originally, White interpreted the problems of sex-chromosome evolution (mainly) by four approaches: the comparison of sizes and shapes of chromosomes at metaphase I, the study of the heteropycnosis
of particular chromosomal regions, chiasma formation on homologous regions at meiosis and comparative studies in different groups (White 1940a,b, 1941a, b, 1960, 1973; Castillo et al.
In the metaphases II with n = 12, the X chromosome was identified through its large size and positive heteropycnosis
During interphase, the observed X chromatin positive heteropycnosis
nitidum exhibits positive heteropycnosis
(greater condensation than autosomes) during the first meiotic division and interkinesis as well as in prophase II.