The DNA sequence of human chromosome 21

Area of Science:

• Human Genetics
• Genomics
• Molecular Biology

Background:

• Chromosome 21, the smallest human autosome, is linked to Down syndrome, a leading cause of intellectual disability.
• Genetic loci for monogenic disorders and predispositions for complex diseases are mapped to chromosome 21.
• Loss of heterozygosity in specific chromosome 21 regions is associated with solid tumors.

Purpose of the Study:

• To report the high-accuracy sequence and comprehensive gene catalogue of the long arm of chromosome 21 (21q).
• To achieve near-complete genomic coverage of 21q and analyze its structural features.
• To identify known, predicted, and pseudogenes on chromosome 21.

Main Methods:

• High-accuracy DNA sequencing of 33,546,361 base pairs (bp) of 21q, achieving 99.7% coverage.
• Sequencing of 281,116 bp from the short arm of chromosome 21.
• Bioinformatic analysis to identify genes, including known, predicted, and pseudogenes, and structural features.

Main Results:

• Achieved 99.7% coverage of 21q with minimal gaps, representing the largest contiguous sequence of human DNA reported.
• Identified 127 known genes, 98 predicted genes, and 59 pseudogenes on chromosome 21.
• Discovered structural features such as duplications and repeat structures in telomeric and pericentromeric regions.

Conclusions:

• The high-quality sequence and gene catalogue of chromosome 21q provide a valuable resource for genetic research.
• Understanding chromosome 21's structure and gene content is crucial for studying Down syndrome and other associated diseases.
• Further analysis of structural variations and gene functions on chromosome 21 will aid in understanding complex disorders and cancer.