How can a DNA microsatellite be co-dominant if microsatellites are Short Tandem Repeats which in turn are typically non-coding?

I’m writing an essay for Molecular Genetics and I have to explain that DNA which doesn’t code protein is not “junk”. I’m trying to figure out what the roles of mini and microsatellites hold for DNA . I have just read that microsatellites are “co-dominant” but have previously read that they make up extragenic/non-coding DNA. Any clarification on this essay subject would be greatly appreciated! Thanks!