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Scientists have mapped the Y chromosome for the first time, a breakthrough that could lead to treatments for male cancers and fertility problems.
The small, stubby Y chromosome distinguishes males from females and has genes in areas that provide instructions for making proteins involved in sperm production and development.
Researchers have now pieced it all together and revealed more than 62 million DNA base pairs — 30 million more than previously identified — and 41 new protein-coding genes that make up the Y chromosome.
It was partially sequenced in 2003, but only 50 percent were discovered.
While the scientists are still in the early stages of their discovery, they said the mapping could detect variants and link them to specific traits that could lead to personalized therapies for genetic diseases.
Scientists have identified more than 62 million DNA base pairs – 30 million more than the previous analysis performed 20 years ago – and 41 new protein-coding genes, instructing our DNA how to assemble them.
Previous research has shown that men can lose some or all of that genetic material as they age, but scientists have never fully understood why this happens and what consequences it might have.
The loss can increase the risk of cancer, heart disease, cancer and Alzheimer’s disease, and a declining sperm count that causes infertility.
Kateryna Makova of Penn State University and collaborator on the study said: ‘The Y chromosome is by far the most difficult human chromosome to sequence and assemble.
‘Deciphering its full sequence is an important scientific milestone. My group has been working on the Y-chromosome for over twenty years and I didn’t think it would be possible to determine its complete sequence in the short term.’
The X chromosome was fully sequenced in 2020 by researchers at NHGRI, who chose to sequence it first because of its link to a range of diseases, including hemophilia, chronic granulomatous disease, and Duchenne muscular dystrophy.
There are 24 chromosomes, including Y and X, resulting in humans having 23 pairs, while other great apes have 24.
The Y chromosome was elusive due to its relatively complex structure. Unlike most other chromosomes, the Y consists of palindromes, or sequences that are the same forward and backward.
The T2T Consortium, which conducted the study funded by the National Human Genome Research Institute (NHGRI), applied new DNA sequencing technologies, sequence assembly methods and knowledge gained from generating the first gapless sequences for the other 23 human chromosomes to solve this mystery.
The 30 million new bases added to the Y chromosome reference (right) will also be crucial for studying genome evolution. The X chromosome (left) was fully sequenced in 2020
Adam Phillippy, senior researcher at NHGRI and consortium leader, said: ‘The biggest surprise was how organized the reruns are.
“We didn’t know what exactly the missing sequence consisted of. It could have been very chaotic, but instead nearly half of the chromosome is made up of alternating blocks of two specific repeating sequences known as satellite DNA.
“It produces a beautiful, quilt-like pattern.”
The 30 million new bases added to the Y chromosome reference will also be crucial for studying genome evolution.
It is now possible to study specific and unique Y chromosome sequence patterns, such as the structure of the two satellites and the location and copy numbers of the genes.
In a second study from the University of Washington, researchers used the reference sequence to assemble 43 me Y chromosomes with roots in Africa.
The team found that the participants shared a common ancestor from about 183,000 years ago Y chromosomes were vastly different in size, ranging from 45.2 million to 84.9 million base pairs in length.
Philip told it Living Science that while developing treatments for diseases related to the Y chromosome may not happen anytime soon, he is optimistic about this achievement.
“This looks like the blueprint we’re looking at, and if it has complete holes in it, you might not even know where to start,” he said. “But by filling them in, we have the complete picture.”