In my Y DNA of R1b1c I have a rare combination of DYS390=23 and DYS391=10. DYS390=23 is usually combined with DYS391=11 and not 10. Is this just an ordinary mutation of DYS391? Or are there any ideas on this value being 10 and not 11. Why is the 23/10 combination so rare? bjornrcs@gmail.com