Re: Genetic Sex change operations?

Anders Sandberg (
31 May 1999 15:06:23 +0200

Darin Sunley <> writes:

> Here's the question. Given a female genome, is there enough info in
> there for a purely typographic process to generate a male genome? Or
> vice versa? Or is it necessary to "ad-lib" the missing parts to change
> the gender that that particular genome will grow into.

As I recall, there is a single gene on the Y-chromosome that starts the differentiation process to a male; if it is missing then XY will produce a female phenotype. Ah, here is what I found at

1.The SRY Gene

-short arm of the Y chromosome contains about 10 million base pairs
(10,000 kb); only possible to isolate and characterize maybe 50 or 100 of these
-by 1986 using "positional cloning" techniques researchers had
isolated TDF to upper part of short arm of Y
-David Page et al at MIT; patients from infertility clinics (no sperm)
-used males, genetically XX with a tiny piece of short arm of Y
translocated onto one of X chromosomes
-1987 first located in 300 kb region, by recombinant DNA techniques
followed by probing, a gene called ZFY (loops of amino acid chains held together with zinc ions)
-detected male-specific fragment in all mammals investigated and was
highly conserved BUT quickly found that some XX men with normal testes (though sterile) lacking ZFY THUS ZFY NOT the TDF
-1990 Goodfellow et al then selected 4 XX male patients with tiniest
fractions of Y (35 kb region) and screened for possible gene sequences
-found only one sequence specific to males, and conserved in other species
-named SRY (sex determining region) of Y chromosome
In support of this claim:

1) several XY patients who are female have mutations in the SRY region
2) mutant line of mice with XY females has deletion of corresponding Sry gene
3) Experiment

-take fertilized mouse embryos, mixture of XX and XY, inject with many
copies of cloned and purified mouse Sry gene
-implant embryos back in mums
-gene will be incorporated into genome and expressed in some but not
all baby mice
-produced 2 XX male mice, these were Sry transgenic but also sterile
(because lacked other missing Y genes) THUS Sry gene is both necessary and sufficient to produce male body type in humans and mice

F How SRY Works

1994 used cloned Sry gene as a probe to detect location in body tissue of Sry messenger RNA
-found gene active only in testis
-used PCR to determine when active - Sry m RNA detected 10.5 - 11.5
days after fertilization
Human SRY: gene codes for protein product which binds to a specific target sequence in the DNA and holds it open in a loop, which could either shut down or open up a whole region of DNA for transcription
-1996: PERHAPS the SRY gene acts not by turning on male-determining
genes, but by turning off female-determining ones (ongoing research)

So if you put SRY into XX, you will get a sterile male (since the original question was the origin of Anakin, I think we can safely say this was not the method in this case due to the existence of the twins :-)

> ObExtropianism: If I were to want to move into a female clonde body for
> a couple years (being male) would the genetic engineers (expert
> systems?) have to exercise creativity in the design of the female body
> created from my genome, or is there a one to one correspondance?

The problem would be to get a compatible clone body in any case; while the overall design is similar for all humans, individual differences are noticeable and would likely appear when you grow a brainless clone body; the sex difference jusrt complicates things a bit more.

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y