Key Difference – Cytogenetics vs Molecular Genetics
Genetic studies explore how characteristics are passed from one generation to the next generation via genomes. Cytogenetics and Molecular genetics are two subbranches of genetic studies, which study chromosomes and genes. The key difference between cytogenetics and molecular genetics is that cytogenetics is the study of number and structure of chromosomes using microscopic analysis whereas molecular genetics is the study of genes and chromosomes at the DNA molecule level using DNA technology.
CONTENTS
1. Overview and Key Difference
2. What is Cytogenetics
3. What is Molecular Genetics
4. Side by Side Comparision – Cytogenetics vs Molecular Genetics
5. Summary
What is Cytogenetics?
Chromosomes are the driving force of heredity in cells. They contain all the genetic information of the organism which is inherited from parent to offspring. Any change in the chromosomal number and structure often results in changes in the genetic information which will pass to the offspring. Hence, the information about entire chromosomes in a cell and chromosomal anomalies are important in clinical genetics and molecular studies. Chromosomal abnormalities normally occur during the cell division and are transferred to the new cell.
Chromosomes are composed of DNA and proteins. Therefore, the changes in chromosomes can disrupt the genes encoded for proteins which will result in wrong proteins. These changes produce genetic diseases, birth defects, syndromes, cancer etc. Studies about chromosomes and their changes come under the term cytogenetics. Therefore cytogenetics can be defined as a branch of genetics which deals with the analysis of number, structure and functional changes in the chromosomes of a cell. There are different techniques performed in cytogenetic analysis as follows.
- Karyotyping – A technique which visualises chromosomes of a cell under a microscope to identify number and structure of the chromosomes.
- Fluorescence in situ hybridization (FISH) – A technique which detects the presence, location and copy numbers of genes in the metaphase chromosomes to diagnose various genetic diseases and chromosomal abnormalities.
- Array-based comparative genomic hybridization – A technique developed to analyse copy number variations and chromosomal abnormalities.
Cytogenetic studies reveal the differences in the chromosomal number and structure. Cytogenetic analysis is normally performed during a pregnancy to determine whether the fetus is safe with chromosomal anomalies. A normal human cell contains 22 autosomal chromosome pairs and one pair of sex chromosomes (total of 46 chromosomes). An abnormal number of chromosomes can be present in a cell; this state is known as aneuploidy. In humans, Down syndrome and Turner syndrome are due to numerical anomalies of chromosomes. Trisomy of chromosome 21 causes Down syndrome and absence of one sex chromosome causes Turner syndrome. Karyotyping is one such cytogenetic technique which identifies above-mentioned syndromes in human.
Cytogenetic studies also provide valuable information for reproductive discussions, disease diagnosis and treatments of some diseases (leukaemia, lymphoma and tumours) etc.
Figure 01: Down syndrome karyotype
What is Molecular Genetics?
Molecular genetics refers to the study of structure and functions of genes at a molecular level. It deals with the study of chromosomes and gene expressions of an organism at DNA level. Knowledge of genes, gene variation and mutations are important for understanding and treating disease and for development biology. DNA sequences of genes are studied in molecular genetics. Sequence variations, mutations in the sequences, gene locations are good information for identifying genetic variation among individuals and various disease identification.
Molecular genetics techniques are amplification (PCR and cloning), gene therapy, gene screens, separation and detection of DNA and RNA etc. Using all these techniques, the studies about genes are carried out to understand the structural and functional variations of genes in the chromosomes at the molecular level. The human genome project is a remarkable outcome of molecular genetics.
Figure 2: Molecular Genetics
What is the difference between Cytogenetics and Molecular Genetics?
Cytogenetics vs Molecular Genetics |
|
| Cytogenetics is the study of chromosomes using microscopic techniques. | Molecular genetics is the study of genes at DNA level using DNA technological techniques. |
| Techniques | |
| Karyotyping, FISH, aCGH etc. are techniques used in this field. | DNA isolation, DNA amplification, Gene cloning, Gene screens etc. are techniques used here. |
Summary – Cytogenetics vs. Molecular Genetics
Cytogenetics and molecular genetics are two subfields of genetics which study chromosomes and genes. The difference between Cytogenetics and molecular genetics lies in their focus; cytogenetics is the study of numerical and structural variations of the chromosomes in a cell while molecular genetics is the study of genes in the chromosomes at DNA level. Both areas are important for understanding the genetic diseases, diagnosis, therapy and evolution.
Reference:
1. “What is Cytogenetics?” Coriell Institute for Medical Research. N.p., n.d. Web. 03 Mar. 2017
2. Li, Marilyn, and Daniel Pinkel. “Clinical cytogenetics and molecular cytogenetics.” Journal of Zhejiang University. Science. B. Zhejiang University Press, Feb. 2006. Web. 03 Mar. 2017
3. Cavalli-Sforza, L. Luca, and Marcus W. Feldman. “The application of molecular genetic approaches to the study of human evolution.” Nature News. Nature Publishing Group, 01 Mar. 2003. Web. 04 Mar. 2017
Image Courtesy:
1. “21 trisomy – Down syndrome” By U.S. Department of Energy Human Genome Program. – (Public Domain) via Commons Wikimedia
2. (Public Domain) via Pixabay