In 2022, researchers at the Stowers Institute for Medical Research helped fill the gaps in the human genome that remained after the landmark DNA sequencing efforts of the Human Genome Project two decades ago. About 8% of the total sequence needed to be filled to produce the first complete human genome sequence. Even then, however, something was still missing because that genome did not contain a Y chromosome.

Now, new research from the lab of Stowers Investigator Jennifer Gerton, Ph.D., has provided important contributions to a collaborative research effort resulting in the first complete assembly of the human Y chromosome, published online August 23, 2023, in Nature.

“Until now, about half of the Y chromosome sequence has been missing in the human reference genome,” said Gerton. “Overall, having the complete human reference genome is going to help us understand chromosome structure, evolution, and disease.”

Assembling the complete, end-to-end human genome — and now the complete Y chromosome — has been the goal of the international, multi-institutional Telomere-to-Telomere (T2T) consortium, which is co-chaired by Karen Miga, Ph.D., from the University of California, Santa Cruz, and Adam Phillippy, Ph.D., from the National Human Genome Research Institute of the National Institutes of Health. Gerton and Tamara Potapova, Ph.D., Research Specialist II in the Gerton Lab, have been active members of the T2T consortium since it was formed in 2017 and are coauthors of the study.

“Sequencing and assembling the human Y chromosome has been challenging because it contains various sequence repeats that are difficult to put together in the correct order,” said Potapova. “Previous assemblies of the Y chromosome were plagued by large gaps of unknown sequences.”