Body of Barr and Polymerase chain reaction (PCR) Gender Tests

[Krissy_Is_A_Gem]

Hi
Can anyone shed some light on these gender tests. Of all places I was speaking to a dotorate in bio chemistry in an english school in Krabi Thailand and he said that being xy is not a definitive test of being male. Apparantly the above tests can be used to identify your true gender.  The tests are used by olympic officials to determine gender.

Krissy

[pebbles]

Females and males only use a single X chromosome, The Barr body is this unused chromosome that is found in everyone of a females cells or cells where more than one X chromosome is present. When you stain the DNA of a Cell under a microscope the inactivated chromosome is physically visible in the nucleus as a dark dark splodge.

If you are "XY" and test positive for barr bodies it means you actually have additional X chromosomes meaning either you have a SRY Translocation (Male genes stuck onto the female chromosome) or are XXY Klineflters syndrome.

PCR is a method we used in labs to amplify a piece of DNA from a sample source So we get abit of double stranded DNA then add DNA polymerase, heat the test tube up to 60'c This causes the double strands to melt then the Ploymerase duplicates the strand turning it back into a double helix and overall doubling the amount of DNA

You can use this to perform various Gene probes for gene mutations.

[Krissy_Is_A_Gem]

Thanks Pebbles
Sounds like you know quite a bit about the subject

[glendagladwitch]

I've heard that there are rare cases of XX males and XY females.

There is a gene that codes for male development (I can't remember the name), and it is usually found on a Y chromosome, but not always, and that it sometimes is found on an X chromosome.

So a simple gene karyotype to determine XX, XY,  or something else is not the end of the inquiry.

Still, I don't think the Barr body is the same thing.  I'd like to learn more about it.  Does it simply determine whether more than one X chromosome is present, regardless of whether the gene for male development is present?

EDIT:  The Olympics used to test for the SRY gene, but they stopped in 2000.

http://en.wikipedia.org/wiki/SRY

http://en.wikipedia.org/wiki/XX_male_syndrome

[pebbles]

Still, I don't think the Barr body is the same thing.  I'd like to learn more about it.  Does it simply determine whether more than one X chromosome is present, regardless of whether the gene for male development is present?

Yes the cells inactivate additional X chromosomes beyond the first with Barr bodies, this happens regardless of the presence of other genes or gender expression.

The SRY is one sex critical forming regions but it is possible to have other genes duplicated or deleted and end up with males without an SRY. Or Females with SRY.

Here is a lecture notes from one of my Developmental biology lectures.
http://www.megaupload.com/?d=ZGFV9GV9

The gene triggers often do have mutations in nature that result in intersex individuals, I don't think it covers AIS.

Yeah I know abit about this because I'm a biology student.