When a portion of a chromosome is lost, the missing piece is referred to as a Deletion or deficiency. It may be terminal if it is produced as one end of the chromosome or it may be intercalary if it occurs from interior of the chromosome. Both results from one or more breaks in the chromosome. The portion of the chromosome retaining the region of centromere will survive and the portion without the Centrosome will be lost after mitosis or meiosis in the resultant cells. During synapsis between structural heterozygotes (one normal complete chromosome and one with a deficeinty), the unpaired region f the normal homologue “buckles out”. Such a configuration is called Deficiency loop or Compensation loop. Loops can be observed in salwary gland chromosomes of Drosophila.
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