## Description

20-mer mask: sense strand track shows starts of 20-mers on the sense strand of the reference genome which are not unique and therefore cannot be used to unambiguously place individual reads. These are the positions where no 'sense' nucleosomal fragment starts can be unambiguously placed from 20 nt reads.

20-mer mask: antisense strand track shows starts of 20-mers on the antisense strand of the reference genome which are not unique and therefore cannot be used to unambiguously place individual reads. These are the positions where no 'antisense' nucleosomal fragment starts can be unambiguously placed from 20 nt reads.

## Methods

## Credits

The data for this track is supplied by the Sidow Lab, and the Fire Lab at the Stanford School of Medicine.
Track display advice provided by Hiram Clawson, UCSC Genome Browser Engineering.

## References

Valouev A, Ichikawa J, Tonthat T, Stuart J, Ranade S, Peckham H, Zeng K, Malek JA, Costa G, McKernan K, Sidow A, Fire A, Johnson SM. A high-resolution, nucleosome position map of C. elegans reveals a lack of universal sequence-dictated positioning. Genome Res. 2008 Jul;18(7):1051-63. Epub 2008 May 13.

Supported oligo ligation detection (SOLiD) sequencing technology from Applied Biosystems.