Ask A Scientist© Molecular Biology Archive

name         Amanda W.
status       student
age          18

Question -   My class is debating the issue of genetically engineering
an embryo to make it a certain sex, in this case male.  In defense of
altering the embryos current sex, the defendant is the claim the father
possesses no y-chromosome to give therefore he will forever produce
female offspring. So, my question is: Is there any possible way that
current or near future technology could produce a male offspring from
such a father or an xx set of chromosomes without the use of artificial
insemenation?
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Reply:  The gene which switches default female, development to male resides
on the Y chromosome and is known as SRY.  There may be a few other genes
associated with maleness on the Y chromosome, but most literature refers to
SRY as the key in determining a male.  There are documented medical cases
where an individual with the genotype XX was phenotypically a male.  In these
cases, the SRY gene had undergone translocation, presumably during
crossing-over, and was improperly carried on the paternal X chromosome.  Thus
fathers' whose sperm carried the altered X parented male children.
Obviously, this is not an ideal solution, as it is yet to be discovered what
other "essential" gene may be lacking due to the loss of the entire Y
chromosome.  Additionally, the reliability of producing boys in subsequent
generations is not established.  However, to answer your question of
producing boys without artificial insemenation, it would not be possible
unless the father was naturally producing an abundance of altered X sperm.
With artificial insemenation, it would be possible to use the father's sperm
and alter it so that all or most X chromosomes did carry the SRY gene.  Also
it would be possible to take an XX zygote and infuse it with the SRY gene,
although the ethics would pose a serious barrier.  The failure rate for the
uptake in a zygote for any specific gene is still very high.  It is much too
high to be acceptable for a human where the results could be disastrous
mutation or death for a viable fetus.

Grbrefel
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I suppose so...The Y chomosome is quite small and along with the SRY gene
does determine maleness but mostly very early in gestation.  It would be
possible to extrachomosomally engineer such proteins to come into play at
the proper times to remain female...remember we all begin as females and
then in the first trimester the sry gene turns on for just a short while
beginning the course towards maleness.

Peter Faletra Ph.D.
Office of Science
Department of Energy
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