As they pass into this position they undergo a longitudinal splitting by which the chromatin in each chromosome becomes divided into equal halves.
From numerous investigations which have been made to trace the chromosomes through the various stages of the nuclear ontogeny of plant cells, it appears that the individuality and continuity of the chromosomes can only be conceived as possible if we assume the existence of something like chromosome centres in the resting nucleus around which the chromosomes become organized fon purposes of division.
Visible differences in the chromosomes have even been observed, especially in insects, which are due apparently to an unequal division by which an additional or accessory chromosome is produced, or in some cases one or two extra chromosomes which differ in size from the others.
I also have a report by Dr. Tartaglia on girls with a chromosome anomaly.
On chromosome 17 is a gene called TP53.