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Human Pangenome Map
News: Recently, a new study has been published in the Nature journal describing a Pangenome Reference Map, built using genomes from 47 anonymous individuals (19 men and 28 women), mainly from Africa but also from the Caribbean, Americas, East Asia, and Europe.
What is a Genome?
The genome is the blueprint of life, a collection of all the genes and regions between the genes contained in our 23 pairs of chromosomes.
Our chromosomes are made up of DNA (Deoxyribonucleic Acid), which is a long string composed of four building blocks called nucleotides or bases (A, T, G, and C). These building blocks are arranged in different combinations and repeated millions of times to create 23 pairs of chromosomes.
The genome provides valuable information about our genetic makeup and helps researchers explore various aspects of human biology and health.
Genome sequencing is the method used to determine the precise order of the four letters and how they are arranged in chromosomes.
Sequencing individual genomes helps us understand human diversity at the genetic level and how prone we are to certain diseases.
To circumvent this, one can have a collective identity card, such as a single genome identity card for everyone living in a region.
What is a reference Genome?
A reference genome or reference map is like a standard map that scientists use when they sequence and study new genomes.
The first reference genome created in 2001 was a significant scientific achievement. It helped scientists discover disease-related genes, understand genetic aspects of diseases like cancer, and develop new diagnostic tests. However, it had limitations and wasn't perfect.
Since then, the reference genome map has been refined and improved to have complete end-to-end sequences of all 23 human chromosomes. However, the finished reference genome map does not represent all of human diversity.
This new study published in Nature changes this, describing the making of the pangenome map, the genetic diversity among the 47 individuals, and the computational methods developed to build the map and represent differences in those genomes.
What is a pangenome map?
The pangenome is a graph of each chromosome, with nodes where sequences of all 47 individuals converge and internodes representing genetic variations.
To create complete and contiguous chromosome maps, researchers used long-read DNA sequencing technologies, which produce strings of contiguous DNA strands of tens of thousands of nucleotides long. This helps assemble the sequences with minimum errors and read through repetitive regions of the chromosomes.
Why is pangenome map important?
The human genome consists of 3.2 billion individual nucleotides, with a 0.4% difference between any two individuals.
A complete and error-free pangenome map will help us understand these differences and explain human diversity better.
It has added nearly 119 million new letters and aided the discovery of 150 new genes linked to autism.
Future pangenome maps that include high quality genomes from Indians will shed light on disease prevalence, help discover new genes for rare diseases, design better diagnostic methods, and help discover novel drugs.
Source – The Hindu