A jawless-fish genome untangles the history of vertebrate genome multiplications

 The discovery and analysis of the genome of a jawless fish, specifically lampreys and hagfish, have provided invaluable insights into the evolutionary history of vertebrates and the process of genome duplications.

Jawless fish, belonging to the superclass ,
are among the most ancient extant vertebrates, with a lineage dating back over 500 million years. Their genome, relatively unchanged over millennia, serves as a living fossil, offering a glimpse into the genomic architecture of early vertebrates.

One of the most intriguing revelations from studying the jawless fish genome is the evidence of two whole-genome duplications (WGDs) that occurred early in vertebrate evolution. WGDs are pivotal events in evolutionary history where an organism's entire genome is duplicated, leading to an increase in the number of genes and genetic material.

The first WGD, known as 1R (1st Round), is believed to have occurred before the divergence of jawed and jawless vertebrates, around 500 million years ago. This event laid the foundation for the genetic complexity observed in modern vertebrates, including humans.

The genome of jawless fish provided critical evidence supporting the occurrence of 1R. By comparing the genomes of lampreys and hagfish to those of jawed vertebrates, researchers identified gene families that showed evidence of duplication in the jawless fish lineage but not in jawed vertebrates.

Furthermore, the jawless fish genome shed light on a second WGD, referred to as 2R (2nd Round), which occurred before the emergence of jawed vertebrates. While 2R was previously inferred from genomic data in jawed vertebrates, the analysis of jawless fish genomes provided direct evidence of this event.

Moreover, studying the jawless fish genome has facilitated the identification of ancestral vertebrate genes and regulatory elements. By comparing the genomes of jawless and jawed vertebrates, researchers can infer which genetic elements have been conserved throughout vertebrate evolution and which have undergone changes. This comparative genomics approach allows for a deeper understanding of the genetic basis of vertebrate traits and the evolutionary innovations that have shaped vertebrate diversity.genome has untangled the complex history of vertebrate genome multiplications, providing evidence for two rounds of whole-genome duplications early in vertebrate evolution. These duplications laid the groundwork for the genetic complexity and diversity observed in modern vertebrates, including humans. By deciphering the genomic architecture of jawless fish, researchers can gain insights into the evolutionary processes that have shaped vertebrate genomes over millions of years.