About the Profession
Cytogenetics is a highly complex specialty area of the clinical diagnostic laboratory. Cytogenetic technologists study the hereditary material at the cellular level by examining the structure and behavior of chromosomes. Chromosomes are the condensed form of the genetic material. Inherited or acquired genetic disorders may occur when there is a change in the number or structural arrangement of the genetic material composing the chromosomes. Cytogenetic analysis is crucial for patient care in providing diagnosis, prognosis, treatment and follow-up for chromosomal genetic disorders.
The cytogenetic technologist examines many cells from an individual's specimen to determine the cytogenetic diagnosis. The patient specimen must contain living cells; the most frequently used tissue types are blood, skin, bone marrow, amniotic fluid, tumors and chorionic villi. Chromosomes, the condensed form of the genetic material, are visible only for a short time period during each cell's lifetime. The technologist performs cell culture, manipulations of the cell cycle, cell harvesting and chromosome banding techniques. This allows visualization and identification of the chromosomes so they can perform analysis using state-of-the-art light microscopes. A sophisticated computer imaging system is used to capture images of the chromosomes from single cells, produce karyotypes and generate reports.
Deviations from the normal chromosome banding pattern can be either present at birth (inherited/constitutional) or acquired later in life. A common constitutional anomaly is known as Down syndrome and occurs when an individual's cells contain an extra copy of chromosome #21. Other common constitutional anomalies include translocations, inversions, deletions and duplications ranging in size from large to just barely visible at the light microscope. Smaller deletions and duplications are detected using molecular microarrays. A common acquired anomaly is an exchange of specific genetic material between chromosomes #22 and #9 in specific cells of an individual's blood. This results in a specific cancer called chronic myelocytic leukemia (CML). Any chromosome may be involved in anomalies and many less well-known disorders are routinely detected. Additional specific chromosomal rearrangements are readily detected and provide a definitive diagnostic for leukemia, lymphoma and many solid tumor disease states. Accurate diagnosis permits disease specific treatment decisions. Periodic cytogenetic monitoring is performed to access response to therapy, residual disease status and prediction of relapse.
In addition to the classical microscopic analysis of chromosomes, many genetic diagnostic laboratories include a molecular unit. Cytogenetic technologists have been leaders in the development of probe technology, FISH (fluorescent in situ hybridization), that is transforming modern diagnostic methods. DNA probes, hybridized to human chromosomes, provide information about gene location, deletion, rearrangement or amplification status. Additional techniques that are used to examine genetic anomalies at the molecular level include Southern blot, PCR (polymerase chain reaction) and microarrays.
Cytogenetic technologists are employed in private laboratories, laboratories associated with teaching hospitals, pediatric hospitals, genetics specialty clinics, gynecological high risk care groups, cancer treatment hospitals, research laboratories of universities and pharmaceutical or chemical industrial companies. They may also work as educators, in sales or marketing or other genetics-related occupations. Experienced cytogenetic technologists may be responsible for the management and operation of cytogenetic laboratories. The work is challenging, much like piecing together a complex jigsaw puzzle.
Occupational Outlook Handbook