Journal of Clinical & Experimental Pathology
Open Access

Cytogenetics is an area of genetics that investigates chromosomal structure, function, and involvement in heredity. It studies the chromosomal content of cells and how chromosomal changes can cause genetic illnesses and diseases. Analyzing the arrangement and function of chromosomes provides essential knowledge into many aspects of life, including development, reproduction, and the cellular basis of disorders such as cancer. As a result, cytogenetics provides an important role in both scientific and clinical research. Chromosomes contain genetic material that is passed down from one generation to the next. They are found in the nucleus of every cell and are made up of lengthy DNA molecules and associated proteins. Cytogenetics began with the discovery of chromosomes in the late 19^th century. Early innovators, such as Walther Flemming, observed chromosomes during cell division (mitosis) with simple microscopes. The field made significant progress in the mid-20^th century, when advances in microscopy and staining techniques allowed scientists to see chromosomes more clearly. This resulted in the invention of karyotyping, which is still used in cytogenetics today.

Human cells have 23 pairs of chromosomes, for a total of 46. These comprise 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes (XX for females and XY for men). Each chromosome contains thousands of genes that encode proteins required for proper development and physiological function. They involve changes in the amount of chromosomes, either an increase or a decrease, which frequently cause developmental problems. Advances in cytogenetics have resulted in the creation of various strong instruments and methodologies for thorough chromosomal examination. These methods are used in both research and clinical diagnostics to discover chromosomal abnormalities. Karyotyping is the process of assembling chromosomes in a uniform pattern to show their number, size, and structure. It involves transforming chromosomes to create a visible pattern of bands, known as G-banding that allows the identification of individual chromosomes and their defects. Karyotyping is commonly used to diagnose genetic problems such as Down syndrome, as well as to discover chromosomal abnormalities in cancer.

Fluorescence In Situ Hybridization (FISH) is a more advanced approach that visualizes specific DNA sequences on chromosomes using fluorescent probes. These probes bind to specific sections of the chromosome, allowing for the detection of minor structural defects that karyotyping cannot detect, such as microdeletions or duplications.

FISH is frequently used for cancer diagnosis, prenatal testing, and the discovery of genetic disorders. Comparative Genomic Hybridization (CGH) is a technique for detecting chromosomal gains and losses throughout a whole genome. It compares a patient's DNA to a reference DNA sample, identifying locations with too much or too little genetic material. CGH has proven an effective method for detecting chromosomal abnormalities in developmental disorders and malignancies, particularly solid tumors. Next-Generation Sequencing (NGS) and Whole-Genome Sequencing (WGS) are transforming cytogenetics by enabling the high-resolution sequencing of whole genomes. These methods can detect a wide variety of chromosomal abnormalities, including structural rearrangements, aneuploidies, and variations in the quantity of copies. NGS is very beneficial in cancer research for detecting somatic mutations and chromosomal changes that cause carcinogenesis.

Cytogenetics plays an important role in detecting genetic abnormalities, prenatal testing, cancer, and infertility. It has many applications in clinical medicine, with cytogenetic procedures increasingly being used to guide treatment decisions and patient care. Cytogenetic procedures such as amniocentesis and Chorionic Villus Sampling (CVS) are used to determine a fetus' chromosomal structure. These tests can discover chromosomal abnormalities such Down syndrome, Edwards’s syndrome, and Patau syndrome. Early diagnosis of chromosomal problems allows improved maternal health and informed decision-making for expecting parents. Cytogenetics can help discover chromosomal abnormalities that cause tumor growth, such as oncogene amplifications or tumor suppressor gene deletions. Cancer development is heavily influenced by chromosomal abnormalities. Many cancers, especially hematological cancers such as leukemias and lymphomas, are defined by unique chromosomal translocations or aneuploidies. The Philadelphia chromosome, which results from a translocation between chromosomes 9 and 22, is an indicator of Chronic Myeloid Leukemia (CML). Detecting these anomalies using cytogenetic techniques becomes essential for cancer diagnosis, prognosis, and treatment planning. Array CGH and NGS are widely used to detect chromosomal abnormalities in cancers such as breast, colon, and lung cancer. In addition to therapeutic uses, cytogenetics is an important tool in experimental research. It advances the knowledge of essential biological processes like cell division, genomic integrity, and chromosomal activity. Cytogenetic approaches are used to investigate the genetic basis of diseases, discover new treatment targets, and create new ways to diagnose illnesses.