It seems you might be thinking of cytogenetics, which is a branch of genetics that studies chromosomes and their role in heredity and disease. Here's a breakdown of what cytogeneticists do:

* Analyze Chromosomes: They examine chromosomes under a microscope to look for abnormalities in their number, structure, or arrangement.

* Diagnose Genetic Disorders: By identifying chromosomal abnormalities, cytogeneticists can diagnose a wide range of genetic disorders, including Down syndrome, Turner syndrome, and Klinefelter syndrome.

* Cancer Diagnosis: Cytogenetics plays a role in diagnosing and classifying certain cancers by identifying specific chromosomal changes associated with different types of tumors.

* Prenatal Testing: Cytogenetic analysis is used in prenatal testing to detect chromosomal abnormalities in the fetus.

* Research: Cytogeneticists conduct research to understand how chromosomes function and how changes in chromosomes can lead to disease.

In short, cytogenetics is a crucial field in genetics that helps us understand the role of chromosomes in health and disease.