导读:看到双胞胎宝贝，没有人不喜欢吧？多么盼望自己也能生出一对双胞胎呀。今天小编就来告诉你，生出双胞胎的奥秘是什么。
Twins, and the reasons behind why some people have them and others don’t, has fascinated scientists for centuries.
双胞胎本身，以及为什么有的人能生出双胞胎有的人却不能，几个世纪以来一直是科学家感兴趣的问题。
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.
双胞胎近年来相对更加普遍了——每100个产妇中就有1对以上双胞胎——已经有证据证明异卵双生与遗传因素有关，但至今还没有人成功鉴别出自发性异卵双生的基因。
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.
研究人员发现了两个与双胞胎有关的基因变异，其中一个基因对女孩的月经初潮年龄、更年期年龄与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.
阿姆斯特丹大学的Hamdi Mbarek博士和Dorret Boomsma教授发现了这项重大突破。
The department established the Netherlands Twin Register nearly 30 years ago and questions about the etiology of twinning are among the most frequently asked by the participants.
这个学院早在约30年前就建立了荷兰双胞胎注册中心，参与者询问频率最高的就是与双胞胎原因相关的问题。
The first gene variant is close to the gene coding for the secretion of follicle stimulating hormone, called the FSHB gene.
第一个基因突变与分泌卵巢激素的基因密码相近，被称为FSHB基因。
This hormone is released by the pituitary, the small brain region that governs almost all major hormonal events in the body
这个激素是由脑垂体分泌的，它是小型的大脑器官，统治着几乎人体所有主激素的分泌。
This gene also has significant effects on fertility measures, including the age of a girl’s first menstruation, syndrome, which is a major cause of infertility in women.
这个基因对生育能力以及女性月经初潮时间和多囊卵巢综合症有显著影响。多囊卵巢综合症是女性不孕的主要原因。
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.
第二个突变与所谓的SMAD3基因相关，它可能与卵巢对卵泡刺激素的反应方式有关。
Both variants result in the multiple follicle growth needed for the development of non-identical twins.
这两个突变都会导致多重卵泡的生长，这是异卵双胞胎的基础条件。
Non-identical twins, medically known as dizygotic, develop from two separate eggs from separate follicles fertilised by separate sperm cells.
异卵双胞胎,医学上是这样定义的：两个不同卵泡中单独的两个卵子，和两颗精子结合发育而成。
Whereas identical twins develop from one embryo that splits in half, dizygotic twinning thus starts with a multiple ovulation.
与之相反，同卵双胞胎是由一个卵细胞一分为二发育而来的，因此异卵双胞胎的起因是超数排卵。
The researchers studied a sample of 1,980 mothers who gave birth to spontaneous dizygotic twins. The mothers were carefully selected to only include mothers who did not receive fertility treatments, such as IVF, which can also lead to twin pregnancies.
这项研究总结了1980名自发异卵双胞胎母亲案例，这些人经过严格挑选，没有接受过试管受精之类的生育治疗，因为试管受精也会导致生育双胞胎。
Their genetic profiles were compared to those from a large group of people who were not related, either as mothers or as family members, to dizygotic twins.
再将这些人的基因档案与大量的非异卵双胞胎母亲或异卵双胞胎的家属的人群作比较。
The findings were then were replicated using the deCODE group in another large population study in Iceland.
冰岛的deCODE研究团队在对另一更大规模的人群进行研究时，也发现了同样的结果。
The relative chance of a mother having dizygotic twins is increased by 29 per cent if she has one copy of the twinning gene - or alleles - at both locations in the genome.
如果一个母亲有在染色体两个参与位置有一个双生基因（或等位基因）的单拷贝，她生育异卵双胞胎的概率就会增加29%。
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.
Boomsma博士表示，“人类早就希望能解开自发性异卵双胞胎的秘密，这一直是科学界和临床研究中重要的课题。”
However, there are still more genes to be found that influence spontaneous dizygotic twinning.
不过，还有很多与自发性异卵双胞胎有关的基因有待发现。
The findings appear in the international scientific journal The American Journal of Human Genetics.
这个研究结果已经发表在国际科学期刊《美国人类遗传学》上。
