Genome scientists have decrypted the biggest chromosome yet, one that’s linked to more than 60 diseases and a form of early onset Alzheimer’s that can hit people in their 30s.

Scientists have already published a draft of the human genome, which now must be refined and analyzed.

The human genome consists of 23 pairs of chromosomes, numbered pretty much according to size. Chromosome 14 comprises more than 87 million pairs of DNA, according to Genoscope, the French research centre that completed its mapping.