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  • While searching for a kidney donor, a Boston woman named Karen Keegan stumbled upon a mystery.

    一位波士頓女性,Karen Keegan在尋找肝臟捐贈者時,突然發現了一個謎團。

  • When her three adult sons underwent genetic testing to determine whether they were a match for kidney donation, the test showed that two of them weren't actually her sons.

    當她讓三名成年的兒子進行基因檢測,決定是否能接受腎臟捐贈時,檢測結果顯示出其中兩人不是她真正的親生兒子。

  • Keegan knew she was her sons' mothershe had conceived and given birth to them.

    Keegan知道她是她兒子的母親,因為她懷孕才生下他們。

  • Figuring there must have been an error, her doctors pursued further testing, only to uncover something even more confusing:

    覺得其中可能是有錯誤,她的醫生說服她進一步檢測,卻只發現更讓人困惑的事:

  • She was her children's biological aunt.

    她是她小孩的親生阿姨。

  • It turned out that Keegan had a second genome in some tissues and organs.

    而事實是Keegan在某些組織和器官內有第二組基因。

  • In other words, some of her cells had a completely different set of genes from the others.

    換句話說,她有一些細胞的基因組合跟其它的細胞完全不同。

  • This second set of genes belonged to her twin sister who had never been born.

    第二組基因屬於她從未出生過的雙胞胎姐妹。

  • This condition, where an individual has two genomes present in the tissues of their body, is called chimerism.

    這種身體組織裡出現兩種基因組合的人,被稱為是嵌合體。

  • The name comes from Greek mythology, where a chimera is an amalgam of three different animals.

    這個名稱來自希臘神話,嵌合體是一個三種不同動物的混合物。

  • Individuals with chimerism might have two-toned skin or hair or different-colored eyes, but most are believed to have no visible signs of the condition.

    有嵌合體的人可能會有兩種膚色或異色瞳,但大多數例子不會有明顯的徵兆。

  • Chimerism can come from a twin in-utero, from a tissue or organ transplant, or happen between a fetus and a pregnant woman.

    嵌合體會出現在子宮裡的雙胞胎、在組織或器官移植或在懷孕女性與胎兒之間。

  • So how exactly does it happen?

    所以這到底是怎麼形成的?

  • In one of the most common forms, a mother and fetus swap cells in the flow of nutrients across the placenta.

    其中最常見的形式是母親與胎兒透過胎盤交換流動的養分細胞。

  • The mother can inherit fetal stem cells, undifferentiated cells that are able to develop into any specialized cell.

    母親可以繼承胎兒的幹細胞,而未分化細胞可以成為任何特化細胞。

  • The fetal cells initially go undetected because the mother's immune system is suppressed during pregnancy.

    胎兒的細胞在一開始不會被發現,因為母親的免疫系統在懷孕時會被抑制。

  • But in some cases, cells with the fetus' DNA persist in the mother's body for years or even decades without being destroyed by her immune system.

    但在某些例子中,有胎兒基因的細胞會在母親的體內存在很多年,甚至到幾十年,都不會被母親體內的免疫系統摧毀掉。

  • In one case, a mother's liver was failing, but suddenly started to regenerate itself.

    在一個例子中,一位母親的肝很衰弱,但它自己突然開始重生。

  • Her doctors biopsied her liver, and found DNA in the regenerated tissue from a pregnancy almost 20 years earlier.

    她的醫生幫她的肝做切片檢查,發現重生的組織中有她快二十年前懷孕的基因。

  • The fetal stem cells had lodged in her liver and specialized as liver cells.

    胎兒的幹細胞存放在她的肝,並特化成她的肝細胞。

  • Karen Keegan, meanwhile, acquired her second genome before she was born.

    與此同時,Karen Keegan在她出生以前就有第二組基因。

  • Very early in her own mother's pregnancy with her, Keegan had a fraternal twin.

    在她母親懷孕的早期,Keegan有個異卵雙胞胎姐妹。

  • Keegan's embryo absorbed some fetal stem cells from her twin's embryo, which did not develop to term.

    Keegan的胚胎吸收了一些她雙胞胎姊妹的幹細胞,後來就沒有形成胎兒。

  • By the time Keegan's fetus developed an immune system, it had many cells with each genome, and the immune system recognized both genomes as her body's own, so it didn't attack or destroy the cells with the second genome.

    直到Keegan生成一套免疫系統,裡頭有很多細胞都有兩種基因組。而免疫系統也認為兩種基因組是她本身的,所以沒有攻擊或摧毀第二組基因的細胞。

  • We don't know how much of her body was composed of cells with this second genomethat can vary from one organ to another, and even between tissues within an organ.

    我們不知道她體內有多少第二組基因組合的細胞。有可能是器官跟器官之間,或是組織與器官之間。

  • Some might have no cells at all with the second genome, while others might have many.

    有些人可能不會有第二組基因的細胞,而有些人可能會有很多。

  • At least some of the egg-producing tissue in her ovaries must have carried the second genome.

    至少在在她卵巢內的排卵組織一定會有第二組基因。

  • Each time she conceived, there would be no way to predict which genome would be involved, which is how two of her children ended up with the genes of a woman who had never been born.

    每次她懷孕,就沒辦法預測哪一個基因組會被加入。這就是為什麼她兩個小孩的基因會屬於一個從沒出生過的女性。

  • This can also happen to fathers.

    這也有可能發生在父親身上。

  • In 2014, when ancestry testing determined that a father was actually his baby's biological uncle, researchers discovered that 10% of the father's sperm carried a second genome from an embryonic twin.

    2014年時,血統測試判定一名父親其實是他小孩的親生舅舅。研究員發現父親的精子中帶有10%的第二組雙胞胎胚胎基因。

  • Cases like this challenge our perception of genetics.

    像這樣的例子會讓我們質疑對基因的觀念。

  • Though there are very few documented cases of chimerism from an embryonic twin, we're all amalgams to some extent, carrying around the different genetic codes of our gut bacteria and even our mitochondria.

    雖然像這樣由雙胞胎胚胎組合的嵌合體紀錄很少,但我們的腸道菌群和粒線體都是帶有不同程度的遺傳密碼混合體。

  • And given that 1 in 8 individual births started out as twin pregnancies, there could be many more people with two genomes, and many more lessons to learn about the genes that make us who we are.

    8分之1人的出生都是從雙胞胎懷孕開始,可能有更多有有第二組基因的人,還有更多去學習組成我們基因的課程。

While searching for a kidney donor, a Boston woman named Karen Keegan stumbled upon a mystery.

一位波士頓女性,Karen Keegan在尋找肝臟捐贈者時,突然發現了一個謎團。

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You could have a secret twin (but not the way you think) - Kayla Mandel Sheets

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    nao 發佈於 2021 年 09 月 22 日
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