Techniques of chromosomal studies

Abstract

Chromosomal analysis has been an area of utmost significance for various cytogenetic and medical studies. The techniques to study normal and abnormal chromosomes which initiated as simple observations under the microscope with and without different types of dyes have now developed into more elaborate and invasive techniques. In the early years of cytogenetics, scientists had a difficult time distinguishing individual chromosomes, but over the years, they continued to refine the conditions for preserving and staining chromosomes to the reproducible standard that is now expected in clinical cytogenetics. In today's procedures, metaphase chromosomes are treated with stains that generate distinctive banding patterns, and chromosome pairs are then arranged into a standardized format known as a karyotype. Over the past few decades, versatile methods based on fluorescence in situ hybridization (FISH) have transformed cytogenetics into a molecular science and provided cytogeneticists with powerful new tools. FISH procedures are now routinely employed in clinical cytogenetics. Although chromosomes may appear to be static structures when viewed under a microscope, cytogeneticists know that chromosomes are actually dynamic assemblies made up of a DNA-protein complex called chromatin. This chapter takes stock of all the prevalent techniques, highlighting the principals involved in each method. Karyotyping, genetic mapping, fluorescence in situ hybridization (FISH), multiplex FISH, spectral karyotyping, flow cytometry, and microarray have been described. New trends in cytogenetics to understand the molecular mechanism have been discussed under new generation sequencing.