Changes in the number of chromosomes and variations in the copy number of
chromosomal regions are described in various pathological conditions, such as cancer
and aneuploidy, but also in normal physiological condition. Our initial view of DNA
replication and mitotic preservation of chromosomal integrity is now challenged as new
technologies allow the observation of mosaic somatic changes in copy numbers of
chromosome regions of different sizes. In the mouse various engineering strategies are
available to better understand the significance of copy numbers in normal physiological
condition. For example, inducing recombination during the G2 phase will allow the
generation of deletions and duplications of regions of interest prior to mitosis. The
effects of copy number variation and segmental aneuploidy can be observed now in
daughter cells and explored in somatic mosaics for large chromosomal regions.
Keywords: Chromosomal engineering, Cre/loxP, deletion, duplication, mosaic
genetics.
