Understanding a human pangenome map

• A recent study published in the Nature journal presents a pangenome reference map.
• The map was created using genetic information from 47 unidentified individuals, including 19 men and 28 women.
• These individuals come from various regions such as Africa, the Caribbean, Americas, East Asia, and Europe.

What is a genome?

• The human genome is the entire set of deoxyribonucleic acid (DNA) residing in the nucleus of every cell of each human body.
• It carries the complete genetic information responsible for the development and functioning of the organism.
• Our genome consists of 23 different strings, each composed of millions of individual building blocks called nucleotides or bases.
• The DNA consists of a double-stranded molecule built up by four bases – adenine (A), cytosine (C), guanine (G) and thymine (T).
• Every base on one strand, pairs with a complementary base on the other strand (A with T and C with G).
• In all, the genome is made up of approximately 3.05 billion such base pairs.

What is a pangenome map?

• The reference genome is a linear sequence. However, the pangenome is a graph.
• A pangenome map refers to the representation and analysis of the collective genetic information present in the genomes of a particular species or a group of related species.
• Unlike a reference genome, which represents a single individual or a consensus sequence, a pangenome map captures the genetic diversity and variation across multiple individuals or populations.

Principle

• The concept of a pangenome recognizes that the genome of a species is not a fixed entity.
• But it consists of a core set of genes shared by most individuals, along with a variable set of genes that are unique or present only in certain individuals or subpopulations.
• This genetic variation can contribute to differences in traits, disease susceptibility, and other biological characteristics.

Why is a pangenome map important?

• A comprehensive picture of the species' genetic content
  • A pangenome map integrates genomic data from multiple individuals or strains of a species to construct a comprehensive picture of the species' genetic content.
  • It includes the identification and classification of core genes shared by all or most individuals, as well as the characterization of variable genes that are present in only a subset of individuals.
  • Hence, a complete and error-free human pangenome map will help us understand those differences and explain human diversity better.
• Helpful for researchers
  • By constructing a pangenome map, researchers can:
    • gain insights into the genetic diversity within a species,
    • study the evolution and adaptation of genes,
    • identify genes associated with specific phenotypes or diseases, and
    • understand the overall genomic architecture of the species.

Pangenome map and India

• The current map does not contain genome sequences from Indians.
• Still, it will help map Indian genomes better against the error-free and complete reference genomes known so far.
• Future pangenome maps may include high quality genomes from Indians, including from many endogamous and isolated populations within the country.
• If this happens, it will shed light on disease prevalence, help discover new genes for rare diseases, design better diagnostic methods, and help discover novel drugs against those diseases.