How Cytogenetics and Molecular Genetics Impact Biological Research
Genetics, as a branch of biology, deals with finding traits in patterns across different species with relation to their immediate and distant ancestors. It is a study that also involves research on the commonalities between species which have diversified with evolution in relation to their gene mapping. The field of genetics is broadly divided in cytogenetics and molecular genetics. Both these branches of genetics are very important in understanding a number of factors like the hereditary disease, evolution, prediction of certain diseases like cancer and predisposition to medical conditions like schizophrenia and diabetes in humans.
Difference Between Cytogenetics and Molecular Genetics
In cytogenetics, the number of chromosomes and their structures are the base of the study. It also involves studying the relation of chromosomes with the behaviour of cells during the process of cell division. Chromosomal deformities and abnormalities fall under the realm of Cytogenetics. 'Chromosomal abnormalities' means an increase or decrease in the number of chromosomes or translocation of one chromosome with another. The chromosomes are inside the nuclei of the cells which are responsible for carrying the genetic information from a parent to the offspring. In Cytogenetics, we can study the link between the changes in chromosomes and a genetic disorder. This field of genetics helps us learn disorders that are either genetically inherited or caused by abnormalities of the chromosomes; Down syndrome, e.g., is a disorder caused by the presence of an extra copy of chromosome 21 in the affected person. Similarly, a girl child born with only one X chromosome has turner syndrome, and an extra X chromosome in a male child causes Klinefelter syndrome due to a total of 47 chromosomes.
Molecular genetics is a molecular level study of chromosomes and segments of DNA is undertaken with the help of DNA technology. Studies like physical examination of a mutated gene fall under the realm of molecular genetics. In molecular genetics, the gene-expression profiling (GEP) helps us determine the level at which genes are expressed in an individual or group. When the field of genetics was in its infantile stage, scientists were baffled whether inheritance was due to the protein or DNA in chromosomes. There were several experiments and researches conducted in which it was proven that dead bacteria can transfer the genetic material to alive bacteria. In another study, it was proven that it was the DNA of viruses that was responsible for infecting the bacteria. This was when it was ruled out that the DNA is the carrier of inheritable information from parent to offspring. This was the preliminary step towards molecular genetics. Later studies went on to discover the types of chromosomes that were linked to the gender of an organism, the number of chromosomes and genes in them etc.
Scope of Studying Cytogenetics and Molecular Genetics
There are a lot of researches done in the field of genetics. Some types of genetic abnormalities and congenital defects that are extremely rare need better understanding with regards to their causes. For instance, atavism is a phenomenon, in which an organism is born with a trait which was lost in the course of evolution; e.g., some human babies are born with tails, a physical characteristic which was lost in the course of millions of years of evolution; detailed genetic scrutiny can help geneticists to determine as to what made the trait reappear and what interplay of which genes made it happen. Such analysis can be a part of both Cytogenetics and molecular genetics; with the help of cytogenetics, a geneticist can understand what all structural and numeric changes have taken place in the chromosome and genes, respectively, as a result of the reintroduction of a dormant gene.
FAQs on Cytogenetics vs Molecular Genetics: What’s the Difference?
1. What is the main difference between cytogenetics and molecular genetics?
The main difference lies in the scale of study. Cytogenetics focuses on the study of whole chromosomes and large-scale chromosomal abnormalities, such as changes in chromosome number or structure. In contrast, molecular genetics focuses on the structure, function, and expression of individual genes at the molecular level, studying the sequence of DNA and RNA.
2. What are the primary laboratory techniques used in cytogenetics versus molecular genetics?
The techniques used in these two fields are distinct and tailored to their specific focus:
- Cytogenetics primarily uses techniques like Karyotyping to visualise and arrange all chromosomes, and Fluorescence In Situ Hybridization (FISH) to locate specific chromosomal regions.
- Molecular genetics relies on techniques such as Polymerase Chain Reaction (PCR) to amplify specific DNA segments, and DNA Sequencing to determine the exact order of nucleotides in a gene.
3. Can you give an example of a genetic condition primarily studied using cytogenetics and one using molecular genetics?
Certainly. A classic example for each field demonstrates their different applications:
- A condition studied using cytogenetics is Down Syndrome, which is caused by an extra copy of chromosome 21 (Trisomy 21). This is a large-scale numerical abnormality visible in a karyotype.
- A condition studied using molecular genetics is Cystic Fibrosis. It results from mutations in the single CFTR gene. The chromosomes appear normal, so molecular techniques are required to analyse the gene's DNA sequence.
4. In what types of medical diagnoses would cytogenetic testing be preferred over molecular genetic testing?
Cytogenetic testing is preferred for diagnosing conditions involving large-scale genomic changes. It is the primary method for identifying aneuploidies (abnormal number of chromosomes), such as in Turner Syndrome or Klinefelter Syndrome, and large structural rearrangements like translocations, deletions, or duplications that are often associated with certain cancers and congenital disorders.
5. How do cytogenetics and molecular genetics complement each other in understanding genetic disorders?
These two fields provide a comprehensive understanding of genetic disorders by working together. Cytogenetics can identify a large chromosomal abnormality, like a microdeletion, but it cannot reveal which specific genes are lost. Molecular genetics can then be used to analyse the deleted region at the DNA sequence level to identify the exact genes involved and understand how their absence causes the specific symptoms of the disorder.
6. What is molecular cytogenetics, and how does it bridge the gap between the two fields?
Molecular cytogenetics is a hybrid field that combines techniques from both molecular biology and cytogenetics. The best example is Fluorescence In Situ Hybridization (FISH). This technique uses a fluorescently labelled DNA probe (a molecular tool) to bind to a specific location on a chromosome (a cytogenetic structure). This allows scientists to visualise the presence, absence, or location of a specific gene or DNA segment on a chromosome, bridging the gap between whole-chromosome and single-gene analysis.
7. How does the scope of work differ for a cytogeneticist versus a molecular geneticist?
A cytogeneticist typically works with cells to prepare, stain, and analyse chromosomes under a microscope, creating karyotypes to detect large-scale abnormalities. Their work is highly visual. A molecular geneticist, on the other hand, works with DNA and RNA extracts, using techniques like PCR and sequencing to analyse gene sequences and expression levels, often dealing with data analysis and bioinformatics to interpret results.
