What is that? Dr Ruchika Irene Dillu explains

What is genome?

The genome is defined as a complete set of genetic instructions that are encoded in a double helix structure formed by base pairs attached to a sugar-phosphate backbone called deoxyribonucleic acid popularly (DNA). Each genome contains all of the information needed to build an organism and allow it to grow and develop.

Evolution of gene mapping

The concept of gene mapping has evolved gradually. Many early discoveries such as the fundamental law of inheritance by Gregor Mendel in the early 19th century, the structure of DNA by James Watson and Francis Crick in 1953, genetic disorder-down syndrome, turner and Klinefelter syndromes first published in 1959 etc. contributed as important milestones to evolve the study of genomes as it is applied today.

The landmark achievement of exploration in history is the human genome project (HGP) which was launched in 1990 and declared essentially completed in 2003 with 80% of the genome. Identification complete genome was achieved in 2021 and final gapless assembly was finished in January 2022. The main goal of the HGP was to map all the genes of human beings and to understand their function. The development of newer, better, cheaper tools and techniques to achieve the goal of HGP was the natural outcome of the development process.

What is gene mapping?

At the simplest level, gene mapping is a method of determining the location of genes on the chromosome. Gene mapping-linkage mapping- provides clues about which chromosome contains the gene and precisely where the gene lies on that chromosome. Various laboratory techniques utilize samples from individual blood, saliva or tissue to isolate DNA from these samples and examine it for patterns that are unique to an individual.

Gene mapping in India

Inspired by the Human Genome Project Department of Biotechnology approved a gene mapping project- Genome India Project (GIP) in 2020. The project aims to build an “Indian reference genome”, based on which the traits of the diverse Indian population could be understood. The project has been described by the researchers as the “first scratching of the surface of the vast genetic diversity of India”.

Genome India Project is a collaborative research project of over 20 universities across the country and is led by the Indian Institute of Science’s Center for Brain Research, Bangalore. The results from this project will collectively facilitate future exhaustive human genetic studies for researchers across India. Such studies are expected to be transformational for the healthcare scenario of the country in the long run.

Application of gene mapping in healthcare

Until now, most medical treatments have been designed for the “average patient.” As a result of this “one-size-fits-all” approach, treatments can be very successful for some patients but not for others. With the advent of modern genomics, phenotypic differences can be mapped to genotypic differences via Precision Medicine.

Precision medicine approaches to cancer have become the prime examples of opportunity that this strategy offers, for example in the pre-genomic era chemotherapy was widely used with variable success. With the evolution of cancer genome sequencing targeted therapies have led to a dramatic change in response to treatment, drug tolerability and improved survival. 19 of the 49 new therapeutic molecular entities US FDA approved in 2020 — as well as a new cell-based therapy — are personalized medicines.

Precision genomic has led to the newer classification of diseases with diverse biology such as dementia. Genetic maps have been used successfully to find the gene responsible for relatively rare, disorders such as cystic fibrosis and duchenne muscular dystrophy. It has also contributed significantly to identifying many genes that are believed to play a role in disease biology and the treatment of more common disorders such as asthma, heart disease, diabetes, cancer, and psychiatric conditions.

Additionally, genetic mapping plays a critical role in modern diagnostic procedures. A well-known example is an antenatal care which helps to establish evidence of the association of diseases that are inherited from parent to child.

Risk of gene mapping

Risks of gene mapping are not limited to:

Genetics discrimination: Discrimination based on genetic make-up in cases of health insurance, employment etc is possible. This could fuel burning questions regarding the indigenous population, race / caste-based politics and origin tracing.

Genome editing: Gene therapy has the potential to treat several diseases, there are ethical concerns regarding the extent to which the same can be employed – a double edge sword that could lead to genetic enhancement.

Privacy: There are privacy issues regarding consent of research participants, usage of the findings and associated risks. There are knowledge and cultural barriers to fully understanding the potential benefits and identifying risks attached to gene mapping. Further, the question of storage and protection of data needs to be addressed considering the possibility of misuse of data.

unequal access: Limited access to genetic testing and preventive medication could further the prevailing inequality and create social tensions.

Take home message

Gene mapping has the potential to transform healthcare using precision medicine: creating wellness awareness, addressing rare genetic disorders, difficult to treat cancer and chronic debilitating disease. However, the various risks and issues associated with gene mapping, storing and usage of genetic data must be addressed and clear policy is drawn for better access, affordability and usage of this novel technology.

(Dr. Ruchika Irene Dillu, MD, Pharmacology)


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