In cytogenetics, DNA and proteins are examined as long strands of DNA that carry most of a cell's genetic information. Cytogenetics is the study of chromosomal alterations in tissue, blood, or bone marrow samples in a laboratory to check for damaged, missing, altered, or additional chromosomes. Changes in specific chromosomes may indicate a hereditary illness or condition, or certain forms of cancer. Cytogenetics can be used to assist diagnose a disease or condition, plan therapy, or assess the effectiveness of treatment.

Researchers can use modern cytogenetic techniques to do the following, among other things:

  • Using various colored dots, precisely designate the chromosomal position of any gene.

  • Examine cells from any tissue, including malignant cells.

  • Determine whether a specific chromosome has lost or gained, whether a specific set of chromosomes has been translocated, or whether a specific gene is lost or gained.

  • Assess the loss or gain of specific chromosomal regions without ever examining them under a microscope.

Clearly, cytogenetics has evolved into an important tool for studying and diagnosing human disease.


Human abnormalities and medical applications

The introduction of procedures for enumerating chromosomes made it easier to discover aberrant chromosomes and chromosome numbers. Cytogenetics revealed that Down syndrome is a simple trisomy, a congenital disorder. When there is a nondisjunction event that causes aneuploidy in one parent or fetus, cells can develop aneuploidy (addition or deletion of entire chromosomes). 

Lejeune made the initial discovery of trisomy 21, usually referred to as Down syndrome, in 1959. 

The number of chromosomes found was also abnormal, as well as sex chromosomes. When a male possesses an extra X chromosome, giving him a total of 47 chromosomes, Klinefelter syndrome develops. Several combinations of sex chromosomes are compatible with live birth, including XXX, XYY, and XXXX. 

Having two copies of the chromosome in normal females requires them to be inactivated, so mammals are able to tolerate aneuploidies in their sex chromosomes. In individuals with extra X chromosomes, there is a phenotypic effect because not all genes on the X chromosome are inactivated.


  • The advent of banding techniques

In the late 1960s, Torbjörn Caspersson invented the quinacrine fluorescent staining method (Q-banding), in which a distinctive banding pattern was observed for each chromosome pair. As a result, distinct horizontal banding patterns allowed chromosomes of otherwise equal size to be distinguished from one another. In chromosome translocations, banding patterns are now used to identify the breakpoints and constituent chromosomes.

In addition to identifying and describing deletions and inversions within an individual chromosome, standardized banding nomenclature can also be used to describe them more precisely. In the early 1970s, a bright field microscope was used to visualize G-banding patterns (using trypsin and Giemsa/Wright stain) simultaneously.

It is called an idiogram when the banding patterns are used to identify the chromosomes. By using these maps, cytogenetics was quickly brought into the clinical lab by both prenatal and oncological fields, where scientists could look for chromosomal variations with karyotyping. In addition to free amniocyte culture, elongation techniques were expanded for all cultures, allowing for higher-resolution banding.


  • Beginnings of molecular cytogenetics

A classical definition of cytogenetics is one that describes the structure of the chromosome and determines how abnormalities contribute to disease. Through cytogenetics, changes in the chromosomes can be identified, such as broken, deleted, additional, or rearranged chromosomes, in blood, tissue, or bone marrow samples.

Although chromosomes are fundamental to biology, scientists only became interested in them in the 1960s when a chromosomal defect caused Down syndrome. Scientists became fascinated by chromosomes and their influence on the disease after this discovery. Cytogenetic studies, which have been conducted since the 1960s, have identified a number of diseases and conditions associated with changes in chromosomes. It is now common for doctors to use cytogenetics in diagnosing, planning treatment, and assessing treatment effectiveness.

Throughout history, the term cytogenetics has evolved in its meaning. Molecular cytogenetics (or comparative genomic hybridization) is a modern scientific term that refers to chromosome research methods such as fluorescence in situ hybridization (FISH) and multicolor fluorescent imaging. There are many applications of molecular cytogenetics, including in vivo imaging, microarrays, nanobiotechnology, real-time polymerase chain reaction (PCR), and single molecule detection.




A powerful new tool for detecting many chromosomal abnormalities has been developed by Fluorescence in situ hybridization (FISH) over the past few decades. As part of the FISH procedure, fluorescently-labeled DNA or RNA probes are hybridized with the complementary DNA sequences on chromosomes. 

The use of spectrally distinct fluorescent dyes for multiple probes in FISH experiments generates colored results. The target DNA sequences either have a single gene or a collection of genes along the length of a chromosome. Clinical cytogenetics routinely emphasizes FISH procedures. Based on spectral microscopy, spectral karyotyping (SKY) examines chromosome rearrangements. 

It requires only one FISH experiment to use specific painting probes for SKY of human metaphase chromosomes. Chromosomal mutations can also be identified by cytogeneticists using locus-specific, chromosome enumeration probes.



During cytogenetics, chromosomes are frozen and images are taken of them at the metaphase stage of mitosis. Karyotyping can be described as a cataloging procedure. Following a cross-check of the systemized record of chromosomes against a standard karyotype, an active search for abnormalities and chromosome aberrations begin. 

Among many other uses, karyotyping can be used in prenatal diagnosis, recurrent miscarriage diagnosis, genetic disease diagnosis, family planning, oncology, etc. Modern Diagnostics Center provides best karyotyping test price in Nepal.



Over karyotyping and FISH, comparative genomic hybridization could be a further advancement in technology. Because of its improved resolution and ability to detect chromosomal alterations without the need for cell cultures, CGH has become a standard practice in the diagnosis of prenatal genetic syndromes.

With array CGH, you can measure CNVs (copy number variations) on a locus-by-locus basis faster and more precisely (with higher resolution) than CGH alone. The Cytogenetics- Perform a prenatal diagnosis simulation by Labster will allow you to gather active participation and involvement from students.


Future of cytogenetics

Recently, several advances have been made in molecular cytogenetics, including automated systems for analyzing FISH results, as well as virtual karyotyping methods, such as comparative genomic hybridization arrays, CGH, and single nucleotide polymorphism arrays.


What do we offer in the Modern Diagnostics Center?

The cytogenetics section has a completely automated scanning and karyotyping microscopy system, as well as a fully automated FISH screening system. All systems are operated and all tests are reported by cytogeneticists who are highly trained and competent.

  • Traditional karyotyping and FISH both identify cytogenetic abnormalities.

  • Methodological improvements in molecular cytogenetics technology have exploded during the last decade.

  • These cytogenetics approaches provide color to the otherwise black-and-white world of bands.

  • Our Karyotyping service is available for cases involving leukemia, gynecology, and pediatrics.

  • Our FISH service offers testing for solid tumors, leukemia, microdeletion syndrome, pre and post-natal syndrome, and other conditions.