B. Inversions and Translocations 1. An inversion alters the position and sequence of the genes so that gene order is reversed. C. Duplications 1. Changes in Chromosome Number A. Categories of Change 1. Aneuploidy is a condition in which the gametes or cells of an affected individual end up with one extra or one less chromosome than is normal.
Polyploidy is the presence of three or more of each type of chromosome in gametes or cells.
It is common in plants but fatal in humans. B. Mechanisms of Change 1. A chromosome number can change during mitotic or meiotic cell division or during the fertilization process. Tetraploid germ cells can result if cytoplasmic division does not follow normal DNA replication and mitosis. I or anaphase II frequently results in a change in chromosome number.