What are mitochondria?

    They are tiny energy-producing structures in the cell, sometimes known as its power plants or batteries.

    What is mitochondrial DNA?

    The vast majority of a cell's DNA exists in the 46 chromosomes of the nucleus, half of which are inherited from the mother and half from the father. A very small amount, including 37 genes, resides in the mitochondria, and is inherited almost exclusively from the mother.

    What are mitochondrial defects?

    Mutations in mitochondrial DNA can cause a wide range of disorders. Some are mild but many are serious, including types of epilepsy, cancer and diabetes, heart, muscle, kidney and liver conditions, deafness and blindness.

    How common are mitochondrial defects?

    They affect up to one in 200 births, but serious, inherited defects are less common, affecting about one in 6,500 births. They are passed from mothers to their children and can sometimes cause disease even when the mother is unaffected.

    How can they be treated or prevented?

    They cannot be prevented and few are easily treatable. Therapies generally concentrate on alleviating symptoms.

    What did the new research involve?

    Scientists took chromosomes from the nucleus of one monkey's egg, and transferred them to the egg of another monkey from which the nucleus had been removed. The new DNA was then fused into place using a viral extract. The resulting eggs carried chromosomes from one monkey, and mitochondrial DNA from another.

    What happened when the eggs were fertilised?

    More than 90 per cent of the modified eggs were successfully fertilised with sperm, and 60 per cent were suitable for transfer to the womb. The success rates are very high for this type of research. A total of four apparently healthy monkeys have been born this way, and all appear to have nuclear DNA from one female monkey and mitochondrial DNA from another.

    How could this help families at risk of mitochondrial disease?

    A woman who knows she is at risk, because she has a mitochondrial disease herself or an affected child, could have her eggs modified this way. Her faulty mitochondria would effectively be replaced by healthy ones from an egg donor, before her modified eggs are fertilised by her partner's sperm.

    什么是線粒體？

    線粒體是細胞內一種微小的產能結構，有時被稱為動力工廠或電池。

    什么是線粒體DNA?

    細胞核內的46對染色體上大量的DNA,都是一半來自父親，一半來自母親。可也有很小的一部分，比如存在于線粒體上的37個基因，卻幾乎是毫無例外地遺傳自母親的。

    什么是線粒體缺陷？

    線粒體DNA突變，可以引發多種病變。有的不太嚴重，但也有很多是非常嚴重的，包括各種癲癇病、癌癥、糖尿病、心臟病、肌肉毛病、腎臟病、肝病、耳聾和眼盲等。

    線粒體缺陷的概率有多大？

    新生兒線粒體缺陷的概率為1/200,但是嚴重的、遺傳的缺陷概率要低得多，大約占新生兒比例的1/6500.他們是由母體傳遞到子女的，有時候，或許母親并未因這種缺陷生病，子女卻有可能患病。

    如何治療或預防？

    事實上，根本無法預防，也很難治愈。現有療法一般也僅限于如何減輕癥狀方面。

    最新研究情況如何？

    科學家從一只猴子的卵細胞細胞核中取出了染色體，植入另一只猴子的卵細胞中，同時將后者的細胞核取出。結果發現，新的DNA像病毒一樣汲取營養，結合后的卵細胞，其染色體DNA是一只猴子的，線粒體DNA是另一只猴子的。

    這種卵細胞受孕之后情況如何？

    改造后的卵細胞，90%以上成功受孕，60%被成功植入子宮。對于這種研究來說，成功率還是非常高的。有四只采用這種方法受精的猴胎，健康生了下來，全都是細胞核DNA來自一只母猴，線粒體DNA來自另一只母猴。

    這一研究對患有線粒體疾病的家庭有何幫助？

    一旦某位婦女發現自己可能患有線粒體疾病，或者已經生了患有線粒體疾病的孩子，就可以將自己的卵細胞照此進行改良。有缺陷的線粒體可以有效地被捐獻來的健康卵細胞的線粒體替代，然后再行受精。