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This quirk of nature has always been interesting to me ever since I watch a CSI episode about it.
It's my understanding that DNA profiles can be obtained by many methods..and IF only mouth swab is done it can be missed....because depending on which fluid is tested IF the person being tested is the survivor of a twin which never developed..that twin's DNA actually melds with the other twin...thus two separate DNA profiles can be within the one two that survived!!
So what is a chimera? A chimera twin is formed in a way which is analogous to non identical twins but with a curious twist. Two separate eggs are indeed fertilized by a sperm cell each BUT once the two eggs are fertilized they then fuse together. Yes, one individual kind of absorbs its brother or sister into itself. This means that the new individual formed has two copies of genetic material from two different individuals. A chimera twin can have different genetic profiles depending on which sample is collected and from which part of their body.
Quote:
A well known case was that of Lydia Fairchild, who needed to prove her biological relationship to her children to get state benefit in the USA. DNA tests showed her husband was the father of the children but that she was not the mother. Eventually, her agonizing battle came to an end when she was found to be a chimera twin. This came to light when she gave birth to another child. A DNA test was conducted on the spot which showed that she was totally unrelated to the baby she just gave birth to.
So how rare is twin chimerism? The answer is “very” with only about 30 documented cases amongst humans world-wide.
Just imagine how this could affect testing a suspect in a case due to DNA left at scene..and voila..gets cleared...Yikes!
Humans[edit]
The Dutch sprinter Foekje Dillema was expelled from the 1950 national team after she refused a mandatory sex test in July 1950; later investigations revealed a Y-chromosome in her body cells, and the analysis showed that she probably was a 46,XX/46,XY mosaic female.[13]
In 1953 a human chimera was reported in the British Medical Journal. A woman was found to have blood containing two different blood types. Apparently this resulted from her twin brother's cells living in her body.[14] More recently, a study found that such blood group chimerism is not rare.[15]
Another report of a human chimera was published in 1998, where a male human had some partially developed female organs due to chimerism. He had been conceived by in-vitro fertilization.[3]
In 2002, Lydia Fairchild was denied public assistance in Washington state when DNA evidence showed that she was not related to her children. A lawyer for the prosecution heard of a human chimera in New England, Karen Keegan, and suggested the possibility to the defence, who were able to show that Fairchild, too, was a chimera with two sets of DNA.[16]
There are a number of different causes of atypical genitalia, with the most common described below. The cause, in many cases, is not known and the disorder appears to occur by chance. Children who are born with atypical genitalia may fall into one of the following groups:
True hermaphroditism - children who have:
Both ovarian and testicular tissues
Both genders' internal reproductive organs
External genitalia that are partially ambiguous
Chromosomes that are either 46, XX, 46, XY, or a mixture (referred to as "mosaic")
Which could very well explain why some grow up as a male..and yet feel female or visa versa?? Thoughts??
Mod cut: Moot, since thread has been moved from one forum to another.
Fascinating stuff and shows how little we really know about both gender and DNA. I read this thinking Lydia Fairchild's case took place inthe 1950s or some less enlightened times. But there they were questioning a woman who's just given birth as to why the baby they JUST SAW COME OUT OF HER has different DNA and the date I saw on her wiki page is 2002!
I also heard there is another way to get 2 different DNA results.... Where a child with some type of cancer was treated & after they had 2 DNAs Anyone know what I heard was true or not? IF true it sure messes up using DNA for anything.
I also heard there is another way to get 2 different DNA results.... Where a child with some type of cancer was treated & after they had 2 DNAs Anyone know what I heard was true or not? IF true it sure messes up using DNA for anything.
Anyone who has a bone marrow transplant will have blood with DNA matching the bone marrow donor. It does not mess up anything as long as the person interpreting the DNA knows the history of the person to whom the DNA is matched.
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