Nobel Prize in Medicine 2022

Context

• The 2022 Nobel Prize for Physiology or Medicine has been awarded to Swedish geneticist Svante Pääbo for his research in the field of genomes of extinct hominins and human evolution.

About:

• Awarded by: The Royal Swedish Academy of Sciences in Stockholm.
• Awarded for: Dr. Svante Pääbo’s discoveries in developing new and innovative methodologies to extract clean DNA from thousands of years old fossils and reading genetic information contained in it.
• Relevance: It will help in understanding the influence of archaic gene sequences from extinct human ancestors over the physiology of present-day humans. For example-

• Denisovans gene EPAS1 confers an advantage for survival at high altitudes which is common among present-day Tibetans. 
• Neanderthal genes affect our immune response to different types of infections.

Genome Sequencing

• Meaning: 
  • It refers to sequencing the entire genome of an organism (DNA/RNA based) with the help of many high throughput sequencing and data handling technologies.
• Major genome sequencing methods:

• The clone-by-clone method: The “clone-by-clone” approach involves first breaking the genome up into relatively large chunks, called clones, about 150,000 base pairs (bp) long. Scientists use genome mapping techniques to figure out where in the genome each clone belongs. 
• Whole genome sequencing (WGS): It does not require a genome map and is a faster method of sequencing.

• It is not suitable for larger genomes like eukaryotic genomes as they have a number of repetitive DNA sequences in which the assembling process is challenging.

• Utility of both: To speed up the genome sequencing process, advantages of both methods are used.

Dr. Svante Pääbo’s research Overview

• Discovery of Denisovans: Denisova were a previously unknown hominin. He concluded that gene transfer occurred from Denisovans to Homo sapiens after they migrated out of Africa around 70,000 years ago. 

• The genome sequencing of Neanderthal: Extinction of Neanderthals around 30,000 years ago was concluded after his sequencing of mitochondrial DNA from a 40,000-year-old bone and comparison with contemporary humans and chimpanzees.

• Neanderthals are the closest relatives of the present-day human species. They lived in Europe and West Asia – as far as southern Siberia and Middle East

• Publishing of 1st Neanderthal genome sequence in 2010: Neanderthal DNA sequences exhibit closer similarity with the DNA of contemporary humans originating from Europe or Asia than to contemporary humans originating from Africa. It suggests interbreeding and co-existence between Neanderthals and Homo sapiens.

• Divergence of DNA sequence: He found greater divergence of the Neanderthal genome to the human reference genome as compared  to any of the 5 present-day human genomes. These are-

• San from Southern Africa
• Yoruba from West Africa 
• Papua New Guinean
• Han Chinese
• French from Western Europe 

Importance of the research: 

• Study of human evolution: He researched hominins which are extinct members of the human lineage and ancient gene flow across human evolution. It will also help in the recognition of the field of evolutionary biology.
• Paleogenomics: Dr. Pääbo’s research has resulted in the rise of a new scientific discipline called paleogenomics. It is the study and analysis of genes of ancient or extinct organisms.
• Technological complexity: It is not easy to amplify and sequence ancient DNA because it is highly fragmented and full of contamination from microbes like fungi and bacteria. Also, ancient DNA is not preserved well in tropical weather conditions like Africa and India.

• Better Funding: The renewed interest in the field will hopefully lead to better funding and more opportunities for researchers. 

Source: TH