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

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 potential management and treatment.

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 heredity material.

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

of chromosomal and chromatid aberrations and the mechanism of formation of these aberrations and breaks for karyotype evolutionary trends, the applications of these processes in both diagnostic and functional scenarios, and potential applications in the assessment of various risks faced by the genetic constitution of eukaryotic cells. The fifth chapter highlights the strengths and weaknesses of employing trophoblastic cells as an interesting model to investigate the role of gene copy number modifications and changes in gene expression that are important for normal versus abnormal cell differentiation. The sixth chapter describes the role of high-resolution next-generation sequencing techniques for detecting and quantifying chromosome abnormalities employed in preimplantation genetic testing. The authors highlight that one-step blastocyst biopsy can improve both blastocyst implantation and live birth rate in in-vitro fertilization patients, suggesting the one-step biopsy method is superior to the two-step method. Finally, the authors remark that the screening of these chromosome abnormalities may reduce embryo implantation failure, early miscarriage, birth defects, developmental delay and intellectual disability. The seventh chapter describes commonly employed methodologies for elucidating chromosomal aberrations, the prognostic impact of recurrent chromosomal abnormalities, and risk stratification in haematological disease genetics. Additionally, this chapter presents various types of chromosomal abnormalities identified in many haematological diseases, such as acute myeloid leukaemia, acute lymphoid leukaemia, myelodysplastic syndrome, multiple myeloma, and myeloproliferative diseases, thus highlighting their role in clinical phenotyping and prognosis. The eighth chapter discusses the employment of conventional cytogenetic and molecular analyses involved in the pathogenesis of acute lymphoblastic leukaemia, one of the most common childhood cancers. The chapter highlights how conventional cytogenetic techniques have undergone significant advancements, emerging into molecular cytogenetic technologies, such as fluorescence in situ hybridization, multiplex ligation-dependent probe amplification, array comparative genomic hybridization, and next-generation sequencing, all of which serve as innovative techniques for diagnosis, risk stratification, disease monitoring, and treatment selection. The ninth chapter reviews advances in cytogenetics and genetics in terms of myelodysplastic syndromes, focusing on the role of the conventional karyotype and new genomic technologies, such as single-nucleotide polymorphism array and next-generation sequencing involved in myelodysplastic syndromes, to discover new genetic alterations and develop targeted therapies. The tenth chapter highlights the importance of the identification of the Philadelphia chromosome in chronic myeloproliferative syndromes in terms of diagnosis and prognosis to improve the quality of healthcare provided to patients. Finally, the book concludes with a chapter reviewing how environmental changes in the frontier of mutations or misregulations of cytokeratin genes are involved in the pathogenesis of innate keratinizing disorders, such as cutaneous tissue fragility, skin hypertrophy, and malignant transformation.

The editors of *Cytogenetics - Classical and Molecular Strategies for Analysing Heredity Material* are enormously grateful to all the contributing scientists for sharing their knowledge and insights in this interdisciplinary book project; they have made extensive efforts in arranging the information of each chapter. We hope that the information presented in this book will meet the expectations and needs of all those interested in the various aspects of cytogenetics, including scientists, physicians, pharmacologists, and students, among others. We especially hope that this book

**V**

will guide those in the field to make new discoveries through employing novel and prior methods of investigation in their future research using an understanding of

**Sonia Soloneski Ph.D. and Marcelo L. Larramendy Ph.D.**

School of Natural Sciences and Museum,

National University of La Plata,

La Plata, Argentina

both basic and applied aspects of cytogenetics.

will guide those in the field to make new discoveries through employing novel and prior methods of investigation in their future research using an understanding of both basic and applied aspects of cytogenetics.

> **Sonia Soloneski Ph.D. and Marcelo L. Larramendy Ph.D.** School of Natural Sciences and Museum, National University of La Plata, La Plata, Argentina

**1**

**Chapter 1**

**Abstract**

discussed in this chapter.

**1. Introduction**

Studies on Basic Chromosome

Chromosomal Association and

Behavior in Mulberry (*Morus* Spp.)

Mulberry leaves are primary food for silkworm, *Bombyx mori* L. to feed silkworms and harvest quality silk cocoons. Mulberry belongs to family Moraceae and includes 60 species found distributed in both Hemisphere. In mulberry, chromosome numbers are varies from 2n = 28 to 22n = 308 (Diploid to Decosoploid) with ploidy level x to 22x. Based on chromosome numbers and meiotic behaviors x = 14 has been considered as basic chromosome numbers of the genus. In the present study, two diploids, two uneuploids, two triploids and two teteraploids mulberry varieties were selected for detailed chromosomal numbers and meiotic behaviors belongs to three species, namely *Morus indica, Morus alba* and *Morus latifolia.* Varieties, Vishaala and Kosen were diploids with 2n = 2x = 28 chromosomes and varieties Ber-S1 and S13 were uneuploids with 2n = 30 chromosomes belongs *Morus indica.* Varieties NAO Khurkul and KPG-1 were triploids with 2n = 3x = 42 chromosomes belongs to *Moru alba* and varieties Kokuso and Icheihei were tetraploids with 2n = 4x = 56 chromosomes. Diploids and uneuploids were showed normal meiosis with high pollen fertility and triploids and teteraploids were showed abnormal meiosis with low pollen fertility, due to virtue of higher ploidy level have been

Configuration and Meiotic

**Keywords:** Mulberry, chromosomes, polyploids meiotic behavior

Sericulture is as an important agriculture-based, labor intensive, exportoriented cottage industry, introduced more than 200 years ago in India. This industry consists of several sectors or processes that are linked to one another like a chain. They are mulberry cultivation, silkworms egg production, silkworm rearing, harvesting of cocoons, silk reeling, twisting and weaving and manufacturing silk fabrics. Mulberry silk is produced from silkworms (*Bombyx mori* L.), which form the base of silk production. Mulberry is a fast growing plant and hence farmers can harvest 5–6 silkworm crops in a year at an interval of 26–28 days. The marginal and

Number, Ploidy Level,

*Koluru Honnegowda Venkatesh*
