The map of the human genome was complete after deciphering the Y chromosome

For years, sequencing the human Y chromosome, one of the two sex chromosomes, has been challenging due to its complex structure. Now a team of more than a hundred scientists has managed to decipher it, an important step towards discovering its true role in development, fertility or cancer.

Complete sequencing of the chromosome associated with male development was the last missing piece in the map of the human genome and its details are presented in two papers in the journal Nature.

Behind this achievement is the T2T Consortium (Telomere to Telomere), the same consortium that published the first complete sequence of the human genome in 2022 in six articles in the journal Science and in a dozen additional papers in other publications.

This near-complete map – which lacked the final “picture” of the Y chromosome – completed the milestone reached 20 years ago, when nearly 92% of the human genome had been mapped, already revolutionizing the biology and science. medicine.

Data from the remaining 8% was provided in 2022, revealing hidden areas important to understanding genetic diseases, reproduction or human diversity. The articles published today in Nature complete the circle.

Full sequencing of the Y chromosome has now been achieved, “finally completing the end-to-end sequence of human chromosomes,” according to a statement from the National Human Genome Research Institute (NHGRI), which is leading the research.

The Y chromosome, along with the X chromosome, is often discussed because of its role in sexual development.

While these chromosomes play a central role, the factors involved in human sexual development are scattered throughout the genome and highly complex, giving rise to the variety of human sex characteristics found in male, female, and intersex individuals. , details from NHGRI and Johns Hopkins University.

These categories are not equivalent to gender, these institutions recall, adding that recent work shows that Y chromosome genes contribute to other aspects of human biology, such as cancer risk and severity.

The Y chromosome was particularly difficult to decipher due to its repetitive molecular patterns; collecting your sequence data is like trying to read a long book in shreds.

New sequencing technology and bioinformatics algorithms have allowed researchers to solve these DNA sequences.

The new data fills gaps in more than 50% of this chromosome, revealing key genomic features that impact fertility, such as factors involved in sperm production.

When scientists and doctors study an individual’s genome, they compare their DNA to that of a reference standard to determine where there are variations, according to the University of California.

Until now, the Y chromosome part of the genome contained ‘big gaps’ that made it difficult to understand the variations and the diseases associated with them.

“If variations are found that have not been seen before, the hope is always that those genomic variants are important to understanding human health,” said Adam Phillippy, consortium leader and NHGRI researcher.

For the researcher, medically relevant genomic variants can help design better diagnostics in the future.

The genome is an organism’s complete set of instructions, a book written with combinations of just four chemical units, called A, T, C, and G (adenine, thymine, cytosine, and guanine); these are called nucleotide bases.

For people, This manual contains about 3 billion base pairs (or letters), which are found on the 23 pairs of chromosomes in the nucleus of all cells. Sequencing means determining your exact sequence in a segment of DNA.

The final sequencing of the Y chromosome adds 30 million new bases to the human genome reference, those responsible summarize.

These databases reveal the existence of an additional 41 genes that activate proteins and provide crucial information for those studying issues related to reproduction or evolution.

The full map of the male sex chromosome has been published in one of the Nature papers. The other reports the sequencing of 43 different human Y chromosomes, representing 21 different populations.

The assemblies provide a more detailed insight into genetic variation throughout 183,000 years of human evolution, revealing new DNA sequences, signatures of conserved regions and insights into the molecular mechanisms that contributed to the complex structure of the Y chromosome. (JO)

Questions and answers from the 2023 Elections