Figure 1. Chromatin diminution in Parascaris univalens. (a) Anaphase of the first cleavage division. (b) Anaphase of the second cleavage division. Chromatin diminution occurs in the upper S₁ cell but not in the lower P₁ cell. (c) Four-cell stage after completion of the second cleavage division. The cells S_1a, S_1b and S₂ give rise to the somatic cells, while the P₂ cell represents the germline. P₀, zygote; C, centromere; E, eliminated chromatin; N, nucleus; P₀-P₂, germline; S₁, S_1a, S_1b, S₂, presomatic cells. From Müller et al. (1996).

Figure 2. Cell lineage of the early embryo of Parascaris univalens. Chromatin diminution is indicated by a broken bar. The germline lineage is drawn in thick red lines. Presomatic cell lineages before elimination are represented in thin red lines and somatic cell lineages in broken red lines. From Müller et al. (1996).

Figure 3. Process of chromatin diminution (in chromosomal breakage region ( CBR)-1; blue box) and of the organization of the DNA in the germline, somatic and eliminated chromatin in Ascaris suum. Chromosomal breakage may occur at many different sites within the CBR-1. This process is followed by the addition of telomeric (TTAGGC)_n repeats to all broken chromosomal ends (hatched portions), and by the degradation of the eliminated DNA in the cytoplasm. The gene localized to the left of CBR-1 (red box) is retained in the somatic genome, but becomes located close to the telomere upon chromatin diminution, whereas the gene to the right of CBR-1 (purple box) will be eliminated from all somatic cells. The different diameter of the white arrows indicates the relative amounts of retained somatic and eliminated DNA upon chromatin diminution. The small arrow on the red box denotes the direction of transcription. Modified from Müller et al. (1996).