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.

什么是线粒体？

线粒体是细胞内一种微小的产能结构，有时被称为动力工厂或电池。

什么是线粒体DNA?

细胞核内的46对染色体上大量的DNA,都是一半来自父亲，一半来自母亲。可也有很小的一部分，比如存在于线粒体上的37个基因，却几乎是毫无例外地遗传自母亲的。

什么是线粒体缺陷？

线粒体DNA突变，可以引发多种病变。有的不太严重，但也有很多是非常严重的，包括各种癫痫病、癌症、糖尿病、心脏病、肌肉毛病、肾脏病、肝病、耳聋和眼盲等。

线粒体缺陷的概率有多大？

新生儿线粒体缺陷的概率为1/200,但是严重的、遗传的缺陷概率要低得多，大约占新生儿比例的1/6500.他们是由母体传递到子女的，有时候，或许母亲并未因这种缺陷生病，子女却有可能患病。

如何治疗或预防？

事实上，根本无法预防，也很难治愈。现有疗法一般也仅限于如何减轻症状方面。

最新研究情况如何？

科学家从一只猴子的卵细胞细胞核中取出了染色体，植入另一只猴子的卵细胞中，同时将后者的细胞核取出。结果发现，新的DNA像病毒一样汲取营养，结合后的卵细胞，其染色体DNA是一只猴子的，线粒体DNA是另一只猴子的。

这种卵细胞受孕之后情况如何？

改造后的卵细胞，90%以上成功受孕，60%被成功植入子宫。对于这种研究来说，成功率还是非常高的。有四只采用这种方法受精的猴胎，健康生了下来，全都是细胞核DNA来自一只母猴，线粒体DNA来自另一只母猴。

这一研究对患有线粒体疾病的家庭有何帮助？

一旦某位妇女发现自己可能患有线粒体疾病，或者已经生了患有线粒体疾病的孩子，就可以将自己的卵细胞照此进行改良。有缺陷的线粒体可以有效地被捐献来的健康卵细胞的线粒体替代，然后再行受精。