Cytogenetics is the study of chromosomes when it relates to disease. Chromosomes are the genetic material which functions as the blueprint of how a cell functions once it's produced. We deal specifically with cytogenetics when bone marrow biopsies are performed for the diagnosis of leukemia to identify specific genetic mutations that we can identify doing a procedure called cytogenetics. Specifically it involves growing up cells from the biopsies and extracting the DNA, or genetic material, and then evaluating each specific chromosome to see if it's normal or abnormal.
 

And there are many methodologies in which that can be done, but the ultimate result is identifying a specific abnormality--a loss of a particular chromosome, an addition of another chromosome the translocation or transformation of one chromosome to another. All these types of mutations or defects can lead to different malignancies. And more so for leukemia's: chronic and acute, than for others.