Appendix A. 
159 
Figure 2: Schematic summary of the principal stages in mitotic cell division, simplified 
to show the movement of just two pairs of chromosomes. (Figure 3-4, page 61, in 
Carlson, B.M. Patten’s Foundations of Embryology. 4*** Edition. New York: McGraw-Hill, 
1981. Figure(s) reproduced with permission of the McGraw-Hill Companies.! 
This process does not always occur flawlessly. Errors, such as 
failure of the chromosomes to separate properly, sometimes produce 
new cells that have the wrong number of chromosomes, a condition 
called aneuploidy (that is, not the true number). One cell may have 
an extra copy of one of the chromosomes while the other cell is 
missing a copy. Such a condition can be detected in 
PRE-PUBLICATION VERSION 
