Help me understand DNA testing

[O'Callaghan]

There are women who are genetically XXX, and multiple X, generally. It's quite an abnormal situation but it does occur. You can read about these sorts of sex chromosome abnormalities on the 'web.

However if a person acquires a Y chromosome at all, they will be physiologically "male" if they survive to birth. XXY is rare, but it does occur, the syndrome is called "Klinefelters Syndrome".

Ah, but to what extent will they be male physiologically? Internally, yes, but not necessarily externally. Apparently there is something called AIS where someone can have ordinary male XY chromosomes but their body cannot respond to male hormones, so they are born female and develop as females, but lack any internal female plumbing of any kind, and instead have undescended you-know-what.

AIS came up in the news because someone suggested that it might apply to the 800m champion, Caster Semenya, but apparently if she had that syndrome she would look and sound like a woman, which unfortunately she doesn't. Some others have suggested she might have another problem called CAH, but that raises other inconsistencies. It all goes to show that, especially if you aren't qualified, you can't diagnose someone by looking at them, especially if they have clothes on.

AIS was only suggested, it seems, because some other athletes who failed a gender test had it (who, BTW, were eventually reinstated, because they can't gain muscle due to testosterone), but it doesn't fit her atall.

Reading the news on this reveals that there are many different syndromes, and a lot of them don't even involve abnormal combinations of chromosomes, although they may not be the right ones for the person's apparent gender.

My apologies for the thread hijack. This has almost nothing to do with using DNA tests to trace your heritage.

[ForresterModern]

Ah, but to what extent will they be male physiologically? Internally, yes, but not necessarily externally. Apparently there is something called AIS where someone can have ordinary male XY chromosomes but their body cannot respond to male hormones, so they are born female and develop as females, but lack any internal female plumbing of any kind, and instead have undescended you-know-what.

AIS came up in the news because someone suggested that it might apply to the 800m champion, Caster Semenya, but apparently if she had that syndrome she would look and sound like a woman, which unfortunately she doesn't. Some others have suggested she might have another problem called CAH, but that raises other inconsistencies. It all goes to show that, especially if you aren't qualified, you can't diagnose someone by looking at them, especially if they have clothes on.

AIS was only suggested, it seems, because some other athletes who failed a gender test had it (who, BTW, were eventually reinstated, because they can't gain muscle due to testosterone), but it doesn't fit her atall.

Reading the news on this reveals that there are many different syndromes, and a lot of them don't even involve abnormal combinations of chromosomes, although they may not be the right ones for the person's apparent gender.

My apologies for the thread hijack. This has almost nothing to do with using DNA tests to trace your heritage.

Doctor hat on.

The AIS you speak of (I am not personally aware of what the acronym stands for) is the same as the series of abnormailities I spoke of more commonly known as testicular feminization syndrome, a genetically XY person who for whatever reason does not manufacture or respond to testosterone as a normal person would. Going back to the discussion earlier, since we all start out as litle females and only develop into males if testosterone effects occur these children/people develop into perfectly nromal little girls who unfortunately find out the genetic truth usuall only in their teenage years when they fail to start their menses by the usual time, and are then chromosomally tested. You can only imagine the psychological stresses this causes on all family and friends involved, especially when the "girls" are told that they are genetically male, and effectively sterile as they lack ovaries and internal female organs but also have atrophic male organs. Interestingly there is a higher proportion of them who have more athletic dispositions than the background female population, which may have something to do with other CNS effects of the XY chromosomes other than testosterone.

CAH is another unfortunate group of genetic enzyme abnormalities where the body lacks a certain ability to metabolize an adrenal hormone from one form to another form, instead leaving excess of the first form circulating to cause excessive effect on the developing body. This usually is in genetic females who get inordinate testosterone effects from the excessive variant hormone (similar to but not identical to testosterone) and thereby become genetic females with some tendency toward inordinate virilization, often leaving newborn babies with "ambiguous genitalia" requiring extensive hormonal and enzymatic evaluation along with chromosome evalutation to determine short and long term therapies, both medical and reconstuructive surgical. Many of these children may also have severe metabolic problems due to coincident salt-wasting problems also related to the excess of the variant hormone.

Hopefully the last of the thread hijacks. Doctor hat off.

Back to DNA testing for heritage tracing, as Gilmore said above it is most useful when one has done as thorough a job as possible to trace one's own paternal lineage backwards as far as can be obtained, then supplement that with the information about potential close relatives that may be divulged by the DNA search, which may allow you to pick up the trail again and connect things by backtracking from there to make your needed lineal connection. Otherwise the DNA tests will give you wild hairs all over the world sometimes, when you are most concerned about a specific lineage in a specific place. The others in the world may share a common distant ancestor but may have no bearing on the tracing of your own paternal ancestral lineage.



Jeff :ootd: