Fundamentals of Molecular Biology - V. I. Rezyapkin 2009

Genome rearrangements
Chromatin diminution

In some living organisms, during the initial divisions following Fertilization, chromosome fragmentation and the elimination of a significant portion of Chromatin occur in the Cells destined to become somatic cells. This process is known as chromatin diminution. Chromatin diminution does not occur in the precursor Cells of the germ line. As a result, somatic and Germ Cells acquire different chromosomal structures and vary in DNA content, which ultimately determines the distinct Functions of these Cell types.

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Fig. 9.13. Chromatin diminution in Cyclops divulsus (A) and Cyclops strenuus (B)

As a result of diminution, up to 85% of the chromatin is excised. In some cases, only the ends of the Chromosomes are eliminated, while in others, internal chromosomal regions are removed (Fig. 9.13). The majority of the eliminated chromatin consists of satellite DNA. This DNA is composed of highly repetitive, non-coding short sequences. At the same time, coding sequences may also be eliminated; consequently, the discarded DNA contains genes essential for The Development of germ cells. Chromatin diminution has been observed in nematodes, copepods (cyclops), and certain insects.



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