By two years of age, none are left, essentially causing " menopause before menarche" .

在患儿两岁时，已基本没有卵细保留，导致“初潮前的更年期”。

Other animals, as well as humans, have been successfully bred through artificial insemination, but perfecting the process in dogs took decades because of the critical timing in fertilization of the female dog's eggs.

对于其它物种以及人类来说，人工精已经非常成熟，但对于狗来说，由于对卵细的精时间有着非常高的要求，所以对于狗的人工精研究持续了数十年的时间。

In any case, the ovaries fail to respond to pituitary LH and FSH and which means that they don't release egg cells normally and produce less estrogen, progesterone, and androstenedione.

在任一情况下，卵巢对垂体LH和FSH均无反应，意味着它们不能正常释放卵细且产生的、孕和雄烯二酮不足。

First, they all start as single-celled zygotes — made from a sperm cell and egg cell combo — that become multicellular embryos: the tiny beginnings of roots, stems, and leaves.

首先，它们都是从单细精卵开始的——由精子细和卵细组合而成——然后变成多细：根、茎和叶的微小开端。

More base pairs and more exons mean that there are more chances for mistakes during meiosis, which is when the egg or sperm are being created.

更多的碱基对和外显子意味着减数分裂时有更多出错的可能，导致生成X染色体上有错误编码序列的卵细或者精子。

Since then it has been shown that these ovarian stem cells can develop into eggs, be fertilised and produce perfectly healthy mouse pups.

迄今已经证实，此类卵巢干细能够分化成为卵细，卵细在精后还能发育成健康的鼠宝宝。

New research into mammal reproductions suggests that in principle it might be possible for humans to conceive children without an egg cell.

哺乳动物生殖领域的最新研究发现，大体来讲，人类可以在没有卵细的情况下繁育后代。

It starts with an unfertilized egg cell, added to a blob of yolk, and squeezed down a stretchy tube called an oviduct.

它始于将未精的卵细添加到一团卵黄并挤压一个称为输卵管的弹性管。

Normally, each egg and sperm cell contains 23 chromosomes, and, when they unite, 23 pairs or 46 in total.

正常情况下，每个卵细和精子含有23个染色体，当它们结合在一起时，总共有23对即46个染色体。

In parthenogenesis, an embryo develops from an unfertilized egg cell that doubles its own chromosome count.

在孤生殖中，由未精的卵细在染色体数目翻倍后发育而来。

Fertilising these eggs for experimentation is forbidden in America.

美国禁止为实验用的卵细精。

Then, they turned the male mouse stem cells into female cells and produced functional egg cells.

然后，他们将雄性老鼠的干细转化为性细，并产生功能正常的卵细。

If getting your genes from one generation to the next is the whole point of evolution, then you'd think the best strategy would be to put a lot of eggs into the female basket.

如果你认为“进化”主要是让你的基因一代一代传下去，那么你可能认为最好的方法应该是让性产生足够多的卵细。

Now these are ready to pair up with an egg cell from mom that has 23 chromosomes as well, totaling to 46 chromosomes, and voila–nine months down the road you've got yourself a baby.

此时，这些细已经准备好与来自母亲的卵细进行配对，卵细同样具有23条染色体，组成总共46条染色体，于是9个月后，你就拥有了自己的宝宝。

Eventually, there's ovulation which is when a single follicle fully matures and ruptures, releasing its egg cell, while the other follicles degenerate and die off.

最终，排卵是指单个卵泡完全成熟并破裂，释放其卵细，而其他卵泡退化并相继死亡。

So an egg cell must be fertilized by a sperm cell to form two full sets of chromosomes.

因此，卵细必须由精子精才能形成两套完整的染色体。

Occasionally, an accident occurs when the egg or sperm cell is forming, creating an extra chromosome number 21.

有时候，在卵细或精子形成时会发生意外，产生出一个多余的21号染色体。

Now, only having one complete X chromosome impacts the female reproductive system by increasing the rate of loss of eggs, which normally happens more slowly.

只有一条完整X染色体会影响女性生殖系统，会加快卵细的丢失速率，而该过程对于正常女性来说通常发生得较慢。

The glowing green cells soon produced a brand new crop of human eggs, according to their findings published this week in Nature Medicine.

他们本周发表在《自然医学》上的结果称，这些绿芒闪烁的细很快制造出了一批人类卵细。

Britain's Human Fertilisation and Embryology Authority, however, will allow it in certain cases.

不过英国的人类精和学管理局将在某些研究中允许给卵细授精。