The landscape of human chromosomes varies widely. This includes many features such as gene number per megabase, GC content, density of SNPs and number of transposable elements. For instance, chromosome 19 has the richest gene content (23 genes per megabase) while chromosome 13 and Y chromosome have the least gene content(5 genes per megabase). http://www.healthknow.info/human_genome_projec t.asp