According to Wikipedia, the X chromosome has approximately 153 million base pairs, while the Y chromosome has only 60 million base pairs. Thus, the difference is roughly 93 million base pairs.

My question is: Could this "extra" 93 million base pairs in virtually every single female cell of the human body slightly contribute to the "extra" relative weight of the female as a whole, in comparison to a male (of course) with a similar amount of cells? Or would this weight be so small that we can consider it negligible?


1 Answer 1



93 million bp/cell x 650 daltons/bp x 10^13 cells/body x 1.66 * 10^-27 kg/dalton = 0.001 kg

So I would say it's not too much of a difference :P

however this ignores the rest of the chromosomal material: histones

  • $\begingroup$ Not too much of a difference, but it's something! Thanks. $\endgroup$ Commented Feb 16, 2012 at 18:24
  • 4
    $\begingroup$ Girls take note, this is not a valid excuse. Seriously though, this difference is exploited in some (albeit minimally effective) techniques to sort sperm for gender selection. $\endgroup$
    – bobtheowl2
    Commented Feb 16, 2012 at 18:50
  • $\begingroup$ Yep. Believe it or not, X sperm swim slower than Y sperm. $\endgroup$
    – jp89
    Commented Feb 16, 2012 at 18:53
  • $\begingroup$ So, what is the difference in weight between X and Y sperm? $\endgroup$ Commented Feb 16, 2012 at 19:28
  • $\begingroup$ Very small. Using the same method as above yields an answer of around 0.1 picograms. $\endgroup$ Commented Feb 16, 2012 at 20:08

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