Contents



Preface

As stated in our previous book *Cytogenetics - Past, Present and Further Perspectives*, published by IntechOpen in 2019, the classical definition of cytogenetics presented in Merriam-Webster, as employed since 1930, is "…a branch of biology that deals with the study of heredity and variation by the methods of both cytology and genetics." The medical definition of cytogenetics includes the study of chromosomes, which are the visible carriers of heredity material. Taken together, these definitions convert cytogenetics into a fusion science that joins cytology (i.e., the

We should consider that more than seventy years have passed since that moment in 1952 when Tjio and Levan discovered the diploid number of chromosomes in humans to be 46. During this time, as can be expected, continuous advances in knowledge have resulted in the development of new techniques, ranging from initial conventional banding techniques to current molecular methodologies. Through combining these traditional and molecular techniques, cytogenetics has emerged as an essential tool in the diagnosis of various genetic disorders, leading the way for

The book presents recent advances and strategies in the field of cytogenetics, paying special attention to methodological achievements developed worldwide that have driven the field forward. The contributors clearly discuss several concepts and approaches useful for understanding chromosomal structure and function at its various levels, highlighting chromosomes as visible carriers of

This book is organized into eleven chapters; it begins with a chapter presenting a detailed karyotyping investigation of three species of mulberry belonging to the genera *Morus* spp., including studies on basic chromosome number, ploidy levels, chromosomal associations and configurations, as well as meiotic behaviours of mulberry varieties. The second chapter presents a complete study analyzing the composition and nature of the heterochromatin in different species of electrical fish from the genera *Gymnotus*, which serves as a representative endemic organism of the Neotropical region. This information helps one to comprehend the genetic structures, evolution, and systematics of the richest and most diverse Neotropical fish groups. The third chapter provides an update regarding the relationship between constitutive heterochromatin and the inactivation of transposable elements, focusing on species of fish from the Amazonian region. The authors show that the species of Amazonian fish analyzed seem to respond dynamically, and with remarkable similarity, to a range of stressful stimuli. The fourth chapter describes conventional and molecular banding techniques routinely employed for detecting and quantifying chromosomal aberrations during DNA sample screening. The authors highlight a number of topics: the karyotype and its components, karyotype trends, evolution and its role in speciation, banding patterns and techniques, chromosome differentiation and linearization, banding applications, detection and analysis of chromosomal aberrations, types

study of cells) with genetics (i.e., the study of inherited variation).

potential management and treatment.

heredity material.
