How to Convert From Gene Location to SNP Location I am new to this. I have an SNP array composed of digits [0,1,2] for chromosome 21. How do I find the start:end locations for the region that is "21q22.11" step by step?
You first need to get the coordinates of the "cytoband" 21q22.11, which I would search for using the UCSC table browser. You need the following settings: 
Clade: Mammal
genome: Human
assembly: 
group: Mapping and Sequencing
track: Chromosome Band
table: cytoBand
region: position chr21
output format: BED

(you can leave other options as default)

That will give you a bed file of cytobands on chr21. You'll need to search (e.g. grep) for your cytoband: q22.11.