Hello, Andrew.
We do not have any tracks that specifically deal with nucleolar organizer regions. It is also beyond the scope of this mailing list for us to speculate as to whether or not the NOR ends where the first BAC begins.
In addition, the following page indicates that the short arms of the relevant chromosomes do not exist on the current human assembly: https://www.iscb.org/cms_addon/conferences/ismb2014/posterlist.php?cat=G (see the second section down, Poster - G02). I verified in the Browser that on these particular chromosomes, no annotations exist in the short arm regions.
Please contact us again at gen...@soe.ucsc.edu if you have any further questions. All messages sent to that address are archived on a publicly-accessible Google Groups forum. If your question includes sensitive data, you may send it instead to genom...@soe.ucsc.edu.
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Steve Heitner
UCSC Genome Bioinformatics Group
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