Do we need to wait till a Zygote forms?


Quite early when combined with IVF.

At present there are two method that are available for use.

The first is genetic testing of preimplantation genetic screening (PGS). A single cell is taken from the embryo and tested for sex by genetic testing. Only the right sex embryo is implanted. http://www.babycenter.com/0_choosing-your-babys-sex-what-the-scientists-say_2915.bc?page=1

The second method is the Ericsson method, which is based on the fact that Y sperm swim faster than X sperm, as the Y sperm are smaller. http://www.babycenter.com/0_choosing-your-babys-sex-what-the-scientists-say_2915.bc?page=2

At present there is also a 3rd method that is used in animals but has not gain FDA approval for human use. And that is sperm sorting using florescence activated cell sorting (FACS). In this method a flow cyctometer is used in conjunction with a non-toxic cell permeable DNA dye. the idea here is to sort sperm based on their DNA content. X sperm have more DNA than Y sperm as the X chromosome is bigger than the Y chromosome. This method is called Microsort https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256056/. Primary concerns is that the DNA might cause DNA damage.

An older method that was greatly used between 1970 to early 1980s to sort sperm by sex was density gradient centrifugation. The idea being X sperm being denser than Y sperm as the X chromosome is bigger than the Y. This method of gender sorting is still available in some IVF clinics but medical studies indicate that the method is ineffective http://www.ingender.com/gender-selection/ericsson/Percoll.aspx

More stuff to read about



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    $\begingroup$ Can you please provide a source showing that X and Y sperm can be separated via centrifuge? $\endgroup$ – Harris Dec 29 '16 at 17:57
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    $\begingroup$ The link to IVF lab in my answer states that they use centrifugation to separate X and Y sperm. Even success rate and the cost that they will charge. However if you want a scientific paper, here is one. <ncbi.nlm.nih.gov/pmc/articles/PMC4169681> Or wikipedia if preferred <en.wikipedia.org/wiki/Sperm_sorting> $\endgroup$ – JayCkat Dec 29 '16 at 18:19
  • $\begingroup$ The Wikipedia article is about general sorting. The paragraph about centrifugation is for sorting by sperm quality, not X/Y. Flow cytometry is the one that can be used for differentiation, stating "...flow cytometry is the only currently used technique able to determine the sex of future progeny...". The second article is interesting, but I'm not sure if it actually indicates that the centrifugation is what's actually used for sorting sperm, rather than mixing and separating out additives, and it seems to indicate that the methods aren't very successful. Someone else should weigh in on that. $\endgroup$ – Harris Dec 29 '16 at 21:21
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    $\begingroup$ Hmm.. while centrifugation of sperm to separate out X and Y sperm has been done for the last 30 years, it appears that the method has fallen out of favor. I will change the answer to reflect this and thrown in more stuff I have read about on this subject. $\endgroup$ – JayCkat Dec 29 '16 at 23:56
  • $\begingroup$ @Jay I mean for a normally combined XX or YY, how do know it is XX or YY after they combine. It is different with we can control which combines with Y. $\endgroup$ – questionhang Jan 2 '17 at 3:53

Before the zygote, there is no individual for which sex can be defined! However, it is possible to know the sex of the future zygote if you know the gametes that are going to fuse.

In humans, just like in all placental mammals (which excl. kangaroos and platypus), sex is defined by sexual chromosomes, where males are XY while females are XX. A mother can therefore only pass on an X (and have no influence on the sex of the offspring) while a father can pass on either an X or a Y which will determine the sex of the offspring. Knowing the paternal gamete (the spermatozoid), one can infer what the sex of the future offspring will be. Of course, in one ejaculate, there are about as many X-bearing gametes than Y-bearing gametes.

Technically speaking, could typically make a karyotype to infer whether chromosome X or Y is being transmitted.

  • $\begingroup$ @SanjuktaGhosh Remi said "possible to know the sex", not "know the possible sex" i.e. if you know what sex chromosome the sperm is carrying, you can tell what zygote will result. $\endgroup$ – Harris Dec 31 '16 at 7:13
  • $\begingroup$ @Remi How to know that technically for a normally combined XX or XY? $\endgroup$ – questionhang Jan 2 '17 at 3:49
  • $\begingroup$ Make a karyotype (info edited in the post). Does this answer your question? $\endgroup$ – Remi.b Jan 2 '17 at 11:04
  • $\begingroup$ @Remi If we do not consider ethics, once a X-Y or a X-X combine, we can find it and do karyotype? $\endgroup$ – questionhang Jan 2 '17 at 11:34
  • $\begingroup$ Do you mean "fuse" (like after fecundation) by saying "combine"? What is "it" in can we find it? You can do a karyotype on any cell (whether haploid or diploid). On diploid human cells you can infer sex from karyotype. On haploid human cell, the concept of sex makes no sense but you can still infer whether the haploid cell carries an X or a Y chromosome $\endgroup$ – Remi.b Jan 2 '17 at 12:10

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