On this website, they are saying that, when using a gel electrophoresis to assess DNA quality, :
High quality genomic DNA should give a major band of 10-20 kb on the gel.
Why is that so? I thought it could be because of the size of the chromosomes, but chromosome X in humans is 156,040,895 bp, which is far from 10-20kb. So why is that threshold of 10-20kb? Is DNA breaking usually in chunks with that size?