A team of more than a hundred researchers from around the world integrated into the Telomere-to-Telomere (T2T) consortium has succeeded in completely sequencing the only mysterious piece left in the human genome, the male sex chromosome.
Unraveling the genetic code of the Y chromosome has been mission impossible for decades due to the complexity of its structure, which is why the only complete human genome that was available until now was that of two X chromosomes. Researchers have discovered 41 genes additional protein coders on the Y chromosome and have deciphered structures of genes thought to play important roles in the growth and functioning of the male reproductive system. According to the work published yesterday in Nature, the sequencing of the male sex chromosome adds 30 million DNA bases to the reference human genome, mostly from satellite DNA (highly repetitive sequences).
The structure of the Y chromosome has been a challenge, among other reasons, because some of the DNA is organized in palindromes (long sequences that are the same forward and backward) and it was complicated to know when the repetitive patterns were reversed. But advances in sequencing technology and bioinformatics algorithms have allowed the T2T team co-led by Karen Miga, a biomolecular engineer at the University of California, Santa Cruz, to solve these sequences.
Specialists explain that the genetic code of the Y chromosome reveals details that can help to understand its role in male development, in fertility or in diseases of genetic origin such as cancer, but also to study human evolution. That's because the Y chromosome, unlike the X, is passed from parent to child with little recombination, so it's easier to track genes from generation to generation and see how they've changed.
When scientists and doctors study a person's genome they compare their DNA to that of a reference standard to see where there is variation. "Before we were blind in some parts of the genome and in different mutations, but now we can see the whole genome and we hope to provide new knowledge about the genetics of many diseases", said Michael Schatz, a professor at Johns Hopkins University who is part of the T2T team.
The Y chromosome is best known for its role in sexual development and spermatogenesis (the production of sperm), and is usually associated with men, although it is also found in intersex people. In addition, recent studies have shown that it contributes to other aspects of human biology, such as the risk and severity of cancer.
The researchers assure that the finding will allow progress in several scientific fields and propose to incorporate complete sequences of the Y chromosome into the genomes that make up the pangenome (genomic information of people of various ancestral origins) to facilitate the understanding of the male sex chromosome in the diversity of the population human
