## Description

This track indicates differences in genome assembly NCBI Build 36 (hg18) when compared to the next version GRCh37 (hg19). Contigs used in this assembly, NCBI Build 36 (hg18), that were not carried forward to GRCh37 (hg19) are shown.

The following color/score key is used:

item color | item score | type of change from hg18 to hg19
--- | --- | ---
| 0 | Contigs in hg18 dropped in the transition to hg19
| 500 | Different portion of the same contig used in hg19 compared to hg18
| 1000 | Updated version of the same contig used in hg19 to correct errors in the hg18 sequence

You can use the score filter to eliminate or include the different categories in the display.

## Methods

The contig coordinates were extracted from the AGP files for the assemblies. Contigs that match the same name, same version, and the same specific portion of sequence are noted as identical in the two assemblies. Contigs not satisifying those identical characteristics are included in this track.

## Credits

The data and presentation of this track were prepared by Hiram Clawson, UCSC Genome browser engineering.