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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?

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up vote 13 down vote accepted


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

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Not too much of a difference, but it's something! Thanks. – LanceLafontaine Feb 16 '12 at 18:24
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. – bobtheowl2 Feb 16 '12 at 18:50
Yep. Believe it or not, X sperm swim slower than Y sperm. – jp89 Feb 16 '12 at 18:53
So, what is the difference in weight between X and Y sperm? – Gianpaolo R Feb 16 '12 at 19:28
Very small. Using the same method as above yields an answer of around 0.1 picograms. – EdoDodo Feb 16 '12 at 20:08

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