Natural and Induced Chromosomal Changes 



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FIGURE 21-2 {Left). Formation of a V- 

 shaped chromosome from two rod-shaped 

 chromosomes. 



HALF (OR RECIPROCAL) TRANSLOCATION 



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RECIPROCAL TRANSLOCATION 



FIGURE 21-3 (Right). Formation of two rod- 

 shaped chromosomes from a V-shaped chromo- 

 some and a Y chromosome. 



quent nuclear division and if the number of 

 genes lost in these pieces is small enough, the 

 absence of these parts may be tolerated 

 physiologically. 



The reverse process, the formation of two 

 rods from a V, necessitates the contribution 

 of a centromere from some other chromo- 

 some. This second chromosome may be the 

 Y (Figure 21-3). Suppose the V is broken 

 near its centromere and the Y is broken any- 

 where. If a eucentric reciprocal translocation 

 then occurs, two chromosomes are produced 

 each having one arm that is derived largely 

 from the Y. Then, later, if paracentric dele- 



PARACENTRIC DELETIONS 



