The genome of sperm cells is packed more tightly than that of fibroblasts. (A) The dependence of the contact probability on the genomic distance P(s) averaged over all chromosomes, compared with P ~ 1/s. The blue line indicates fibroblasts (P ~ s-1.27), and the green line indicates sperm cells (P ~ s-1.07). (B) The ratio between sperm cells’ and fibroblasts’ contact probabilities at different genomic distances. The x-axis indicates genomic distance, and the y-axis indicates the ratio of contact probabilities. The black lines show a 1:1 ratio.