​Cytogene​tics​

Cytogenetics is the study of chromosomes and their behavior by using banding or manipulating techniques. The changes in the chromosome relate to the cell behavior. Cytogenetics is the branch of biology that studies chromosomes and their behavior.

Cytogenetics uses manipulating or banding techniques to see the changes in the chromosomes. In this article, we will read about cytogenetics, its application, techniques, importance, and impact on the future, and much more.

Define Cytogenetics

Cytogenetics is a branch of genetics that is used to study the structure and the behavior of chromosomes using various techniques. It involves karyotypes, chromosome bands, and cell division.

What is Cytogenetics?

The branch of biology that studies the behavior of chromosomes mainly during meiosis is known as Cytogenetics. It plays an important role in understanding the abnormalities in chromosomes that can cause genetic disorders or cancer. Walther Flemming, a German anatomist, is the founder of cytogenetics. Chromosomes are thread-like structures located inside the nucleus and were discovered by Swiss botanist Karl Nageli. Each chromosome is made up of protein and a molecule of DNA. the main function of the chromosome is to carry genetic information in a cell. There are 23 pairs of chromosomes in humans out of which 22 pairs are body chromosomes and 1 pair is the sex chromosome that determines the sex of the organism.

History of Cytogenetics

It was Swedish botanist Nageli in the 1840s who first identified thread-like structures in the nuclei of plant cells which he named “Transitory cytoblasts” which are now known as chromosomes. Later in 1843, a German anatomist named Walther Flemming studied the cell’s heredity material and the chromosome and hence he was known as the Father of Cytogenetics.

Techniques of Cytogenetics

Cytogenetics uses various techniques to study the chromosomes in tissues, blood, bone marrow, and culture cells. It can identify structural changes like deletion, insertion, translocation, or numerical abnormalities in the chromosome. Some of the techniques used are:

Karyotyping

In this technique, the cells are first cultured and are arrested in the metaphase stage in cell division and are stained using Giemsa dye and viewed under the microscope. The main purpose of the technique is to examine the complete set of chromosomes and check any abnormalities in the chromosome.

Fluorescent In Situ Hybridization (FISH)

Fluorescently dyed DNA probes are bound to a specific sequence of the chromosome and are viewed under a fluorescence microscope. This technique is mainly used to identify specific chromosomal abnormalities like duplications, translocations, and microdeletions.

Comparative Genomic Hybridization (CGH)

In this technique, the DNA samples from a test and reference sample are dyed separately with fluorescent dyes and these are then hybridized to arrays of DNA sequences, and the fluorescent intensity ratio of the test and reference DNA is measured.

G-Banding

The chromosomes are treated with a solution that partially digests the chromosome and is stained with Giesma dye. This reveals dark and light bands on the chromosome and it is called banding. This banding is mainly used to identify structural abnormalities like deletions, duplications, and translocations in the chromosome.

Array Comparative Genomic Hybridization

The DNA samples are compared on a microarray chip that contains many DNA probes. The difference in DNA sequence between the reference sample and the test sample is measured. With this technique, even a small deletion in the chromosome can be identified.

C-banding

This technique is used to identify the heterochromatin by denaturing the chromosomes with an alkaline solution and staining by Giemsa stain. The heterochromatin is stained dark and it could be visible near the centromere.

R-banding

This technique is the opposite of G-band staining and is also known as reverse chromosome banding. The slides are first incubated in phosphate buffer and stained with Giemsa dye. This technique is mainly used to analyze the structure of the chromosome ends.

Spectral Karyotyping

It is a molecular cytogenetic technique that allows scientists to observe all the chromosomes at once. This technique was developed in 1996 using the probes of chromosome-specific FISH. it identifies the differentiation of the chromosomes based on their spectral properties.

Multicolor FISH

This is used to identify, classify, and assess complex chromosome rearrangements and numerical aberration using a single hybridization.

Genomic Microarray Analysis

This technique uses the genomic DNA to analyze unbalanced rearrangement in the chromosome. It can detect whether there is an extra copy of DNA and identifies its abnormalities.

Molecular Cytogenetics

It is a biomedical science that studies chromosomes at the molecular level and through their life cycle. It involves molecular biology and cytogenetics.

Applications of Cytogenetics

Cytogenetics mainly studies chromosomal abnormalities and is used in several applications:

Genetic Disorder Diagnosis and Treatment

Cytogenetics is a powerful diagnostic tool to identify any genetic abnormality like aneuploidy, down syndrome, and structural abnormalities using techniques like karyotyping, FISH, CGH, and microarray analysis. This identification will help in treating genetic disorders by giving personalized medicine, stem cell therapy, and gene therapy. The disease can be managed by preventive measures and counseling.

Cancer Research and Diagnosis

Cytogenetics is used as an essential tool to diagnose the types of cancer whether they are leukemia or lymphoma or solid tumors. The chromosomal abnormalities like deletions, translocations, amplifications, and additions that are specific to a type of cancer are identified, and the necessary treatments can be given.

Prenatal screening

Cytogenetics is used in prenatal screening to check for any chromosomal abnormalities in the embryos and fetus. The techniques like amniocentesis and chorionic villus sampling, karyotyping are used to diagnose trisomy 21 (down syndrome) in the fetus.

Pharmacogenetics

The understanding of the genetic makeup of an individual helps to provide personalized gene and drug therapy and cytogenetics helps to identify how the individuals react to the drug response.

Stem cell research

Cytogenetic analysis is used in stem cell therapy that ensure the genetic stability of stem cells, especially in regenerative medicine.

Plant and Animal breeding

In animal husbandry and agriculture, cytogenetics is used in breeding programs to select the desirable traits and ensure genetic diversity.

Biotechnology and genetic engineering

Cytogenetics gives a foundation knowledge for biotechnology and genetic engineering applications that include gene editing techniques like CRISPR/Cas9.

Importance of Cytogenetics

The study of chromosomes is important for various reasons like

• Detect chromosome abnormalities: The abnormalities in the chromosomes like addition, deletion, and translocation can be detected and their impact on the genetic makeup can be detected using cytogenetics.
• Characterizing new alterations in the chromosomes: The impact of the altered chromosome and the disease caused due to the alteration can be studied
• Diagnosis and long-term treatment for genetic diseases: Personalized treatment for the specific genetic disease can be provided.
• Predicting the responses to the therapeutics: The response of the drug given for the genetic disease can be predicted
• Genetic counseling: Counseling can be given to patients regarding their disease and the necessary treatment.
• Classifying cancer types: Different types of cancer can be identified using cytogenetic methods.

Future of Cytogenetics

The future of cytogenetics will be a combination of cytogenetics and molecular biology with powerful methods. The methods might include:

• Topological informatics: Using this technique the structural and spatial aspects of chromosomal and genetic data can be studied. The chromosomal structural variations, such as translocations, inversions, and duplications can be studied.
• Spatial transcriptomics: This technique is used to study chromosomal abnormalities and their relation with genetic diseases, how they impact gene expression patterns, and cellular organization within tissues.
• Cellular information management: This technique organizes, analyzes, stores, and interprets genetic and chromosomal information obtained from cells. This is required for cytogenetic studies as it contains vast information about the genetic makeup, chromosomal structure and abnormalities and
• Sensitive in situ hybridization: Sensitive in situ hybridization is a cytogenetic technique that has high-resolution detection, and localization of nucleic acid targets within the cell or tissue. It uses sequence-specific fluorescent probes that are complementary to the target inside the cell.
• In situ sequencing (ISS): This is a powerful tool used in molecular biology and cytogenetics to study the spatial organization of genes and transcripts within cells and tissues. This technique is not like the traditional method that provides genetic information in bulk but in the ISS technique, the DNA and RNA sequences of individual organisms can be studied directly.

These techniques will help to develop personalized medicines for genetic diseases.

Challenges and Limitations in Cytogenetics

Though cytogenetics has advanced significantly in medical diagnostics and treatments, it also faces many challenges and limitations. Some of them are:

• Detection limits
• Complexity in the chromosomal abnormalities
• False positives/ negatives
• Cost and accessibility
• Ethical and privacy issues
• Technological limitations
• Sample quality and handling
• Training and expertise
• Time-consuming

Conclusion- Cytogenetics

Cytogenetics is the branch of cell biology that is used to study the behavior of chromosomes and their abnormalities. It is used in various felids like gene therapy, cancer diagnosis, genetic disease identification, stem cell therapy, pharmacogenomics, and in plant and animal husbandry. The future of cytogenetics will be a combination of cytogenetics and molecular biology with powerful methods. The abnormalities in the chromosomes like addition, deletion, and translocation can be detected and their impact on the genetic makeup can be detected using cytogenetics.

FAQs – Cytogenetics

What is Cytogenetics is used for?

Cytogenetics is the study of chromosomal abnormalities in tissue, blood marrow, or culture cells using banding or manipulating techniques.

Who is the Father of Cytogenetics?

Walther Flemming is known as the father of cytogenetics, a German anatomist who first discovered the behavior of chromosomes in the cell nucleus during cell division.

What is the Difference between Cytogenetics and Molecular Genetics?

Molecular genetics is the study of chromosome and DNA at the molecular level using DNA technology whereas cytogenetics is the study of chromosomal behavior via microscopic analysis.

What is the Purpose of Cytogenetics?

The main purpose of cytogenetics is to study the chromosomes and their behavior. This technique can identify the structural and numerical abnormalities of the chromosomes

What is the Principle of Cytogenetics?

The Principle of Clinical Cytogenetics is an important reference book for all clinical cytogenetics that answers the most frequently asked questions about chromosomes and its diseases.

What are the Different Types of Cytogenetics?

The different types of cytogenetics are Classical cytogenetics, Molecular cytogenetics, Karyotyping, In situ hybridization, Microarray

What is the Difference between Cytology and Cytogenetics?

Cytology is a branch of biology that studies cell structure, life cycle, and pathology. Cytogenetics is the study of the chromosome and its behavior.