胚胎的性别早在受精时就决定了。
胚胎研究是个让人情绪激动的问题。
许多人反对用胚胎做实验。
全国各地的诊所里有24000个冷冻胚胎。
There are 24,000 frozen embryos in clinics across the country.
这篇论文对如何通过克隆制造人类胚胎提供详细的描述。
The paper provides a detailed description of how to create human embryos by cloning.
例如，蛇的胚胎会生长出后肢。
这关系到胚胎在哪个平面被切割。
蝾螈胚胎却会吸引藻类进入组织和细胞。
A salamander embryo can attract algae inside its tissues and cells.
哪些胚胎细胞是确定的？
他从胚胎的耳朵部分中，取出一个泡囊移植到腕部。
Who took a ball, the vesicle, and he transplanted from the embryo, the ear region, to a limb.
更奇怪的是，一个从分裂胚胎中受孕的妇女可以生下自己的双胞胎。
Even more bizarre, a woman conceived from a split embryo could give birth to her own twin.
和我们之前谈到的胚胎干细胞有所不同，这是一个成人干细胞的例子。
Different from the embryonic stem cell we talked about before, it's an example of an adult stem cell.
例如，父母可以将一个胚胎植入母亲的子宫，无限期地储存同卵双胞胎。
For example, parents could have one embryo implanted in the mother's womb and store its identical siblings indefinitely.
胚胎干细胞如此让人激动是因为它的天然功能就是分化成身体所有的细胞。
Why people are so excited about embryonic stem cells is because in nature they become all the cells of the body.
如果在一个不同于早期研究人员所使用的平面上切割，就不会形成两个完整的胚胎。
If it is cut in a plane different from the one used by the early investigators, it will not form two whole embryos.
暂停胚胎的发育比与其兄弟姐妹竞争更有利于使它做好准备以避免艰难时期的到来。
The pause of the development of an embryo has more benefits for preparing it to avoid the harsh times than for competing with its siblings.
这使她能够在干旱和食物短缺时暂缓胚胎的发育，直到育儿袋里的后代能够独立生活。
This allows her to freeze the development of an embryo during times of drought and food shortage until the offspring in the pouch is able to leave.
这使他们相信早期胚胎中的细胞是不确定的，因为每个细胞都有可能以各种不同的方式发育。
This led them to believe that the cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways.
由此产生的杂交后代长成了一个名为胚泡的小胚胎，被植入代孕母亲的子宫，然后变成了多莉。
The resulting hybrid grew into a tiny embryo known as a blastocyst, implanted into the womb of a surrogate mother, and went on to become Dolly.
在其他好处中，这使她能够在干旱和食物短缺时期冻结胚胎的发育，直到育儿袋中的后代有能力自己离开。
Among other benefits, this allows her to freeze the development of an embryo during times of drought and food shortage until the offspring in the pouch is able to leave.
果蝇在家中招人讨厌，但却是一个历史悠久的实验对象。通过研究果蝇，科学家们得以揭开胚胎发育的秘密。
Studying the fruit fly, a household nuisance but a time-honored experimental subject, has enabled the secrets of how embryos develop to begin to be unraveled by scientists.
在北美，南美以及其他一些地方生产的精子和克隆动物胚胎，其在国际范围内的交易已经无法加以有效监管。
The international trade in semen and embryos from cloned animals created in north and south America and beyond was effectively impossible to police.
其他的表观遗传过程似乎是随机发生的，而其他过程则是正常的，比如那些引导胚胎细胞成为心脏、大脑或肝细胞的过程。
Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryonic cells as they become heart, brain, or liver cells, for example.
最成功的陆生植物群体是那些进化出了受精性细胞散布方法的群体，这些方法不依赖于水和防止发育中的胚胎干涸的结构。
The most successful groups of land plants are those that evolved methods of fertilized sex cell dispersal that are independent of water and structures that protest developing embryos from drying out.
近一个世纪前，生物学家发现，如果他们在无脊椎动物胚胎生命的早期阶段将其分成两部分，它会存活下来并发育成两个正常的胚胎。
Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos.
在受精后大约六七个星期时，男性和女性胚胎之间没有什么差别。
For about six or seven weeks after conception, there is no differentiation between male and female.
许多物种的早期胚胎具有其祖先的特性。
因为现今的联邦法律已经禁止使用联邦基金克隆胚胎用于研究或者有意地威胁胚胎的生命，NBAC在胚胎研究上将保持沉默。
Because current federal law already forbids the use of federal funds to create embryos for research or to knowingly endanger an embryo 's life, NBAC will remain silent on embryo research.
冷冻损伤胚胎的确切数目各不相同。
在黄体降解的母羊中，可用的胚胎恢复率非常低。
Useable embryo recovery was significantly low in ewes of corpora lutea degradation.
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