想要雙胞胎?得問問你的基因答應不答應!

Twins, and the reasons behind why some people have them and others don't, has fascinated scientists for centuries.
雙胞胎本身，以及爲什麼有的人能生出雙胞胎有的人卻不能，幾個世紀以來一直是科學家感興趣的問題。

They are relatively common - occurring once in 100 pregnancies - and while the cause of non-identical twins has been linked to genetics, the genes involved had not been identified until now.
雙胞胎近年來相對來說更加普遍了，每100個產婦中就會有1位懷有雙胞胎。雖然已經有證據證明異卵雙生與遺傳因素有關，但至今還沒有人成功鑑別出自發性異卵雙生的基因。

Researchers have pinpointed two gene varians related to twinning, and one can play a major role in the age of a girl's first period, age at menopause and infertility.
研究人員已經發現了兩種與雙胞胎有關的基因變異，其中一種對女孩的月經初潮年齡、更年期年齡與生育能力起着非常重要的作用。

The breakthrough was made by Dr Hamdi Mbarek and Professor Dorret Boomsma from the Vrije Universiteit in Amsterdam.
這項重大突破是由阿姆斯特丹大學的哈姆迪·穆巴拉克博士和多雷特·博穆薩教授發現的。

The first gene variant is close to the gene coding for the secretion of follicle stimulating hormone, called the FSHB gene. This hormone is released by the pituitary, the small brain region that governs almost all major hormonal events in the body.
第一個基因的突變與分泌卵巢激素的被稱爲FSHB的基因密碼相近。該激素是由負責着幾乎人體所有主激素分泌的腦垂體分泌的。

The second variant relates to the so-called SMAD3 gene and is likely to be involved in the way the ovaries respond to follicle stimulating hormone.
第二個突變與所謂的SMAD3基因相關，可能與卵巢對卵泡刺激素的反應方式有關。

Both variants result in the multiple follicle growth needed for the development of non-identical twins.
這兩個突變都會導致多重卵泡的生長，這是異卵雙胞胎的基礎條件。

Non-identical twins, medically known as dizygotic, develop from two separate eggs from separate follicles fertilised by separate sperm cells. Whereas identical twins develop from one embryo that splits in half, dizygotic twinning thus starts with a multiple ovulation.
醫學上定義的異卵雙胞胎，是指兩個不同卵泡中單獨的兩個卵子，和兩顆精子結合發育而成。與之相反，同卵雙胞胎是由一個卵細胞一分爲二發育而來的，因此異卵雙胞胎的起因是超數排卵。

Discovery of the main genes behind the mystery of spontaneous dizygotic twinning was long awaited, and is of great scientific interest and clinical importance,' said Professor Boomsma.
博穆薩教授表示：“人類早就希望能解開自發性異卵雙胞胎的祕密，這一直是科學界和臨牀研究中重要的課題。”

However, there are still more genes to be found that influence spontaneous dizygotic twinning.
不過，目前還有很多與自發性異卵雙胞胎有關的基因有待發現。