[求助]大全36

Protein synthesis begins when the gene encoding a protein is activated. The gene’s sequence of nucleotides is transcribed into a molecule of messenger RNA (mRNA), which reproduces the information contained in that sequence. Transported outside the nucleus to the cytoplasm, the mRNA is translated into the protein it encodes by an organelle known as a ribosome, which strings together amino acids in the order specified by the sequence of elements in the mRNA molecule. Since the amount of mRNA in a cell determines the amount of the corresponding protein, factors affecting the abundance of mRNA’s play a major part in the normal functioning of a cell by appropriately regulating protein synthesis. For example, an excess of certain proteins can cause cells to proliferate abnormally and become cancerous; a lack of the protein insulin results in diabetes.

Biologists once assumed that the variable rates at which cells synthesize different mRNA’s determine the quantities of mRNA’s and their corresponding proteins in a cell. However, recent investigations have shown that the concentrations of most mRNA’s correlate best, not with their synthesis rate, but rather with the equally variable rates at which cells degrade the different mRNA’s in their cytoplasm. If a cell degrades both a rapidly and a slowly synthesized mRNA slowly, both mRNA’s will accumulate to high levels.

An important example of this phenomenon is the development of red blood cells from their unspecialized parent cells in bone marrow (bone marrow: n. 骨髓). For red blood cells to accumulate sufficient concentrations of hemoglobin (hemoglobin: n.血色素) (which transports oxygen) to carry out their main function, the cells’ parent cells must simultaneously produce more of the constituent proteins of hemoglobin and less of most other proteins. To do this, the parent cells halt synthesis of non-hemoglobin mRNA’s in the nucleus and rapidly degrade copies of the non-hemoglobin mRNA’s remaining in the cytoplasm. Halting synthesis of mRNA alone would not affect the quantities of proteins synthesized by the mRNA’s still existing in the cytoplasm. Biologists now believe that most cells can regulate protein production most efficiently by varying both mRNA synthesis and degradation, as developing red cells do, rather than by just varying one or the other.

请帮忙讲解一下这三道题好吗？我晕晕的了。

我看了你的问题也觉得头晕了。谁能回答你这么多的而且又是非具体的问题啊？：）只好将就先把文章看看了。至于问题，需要楼主具体解释一下自己的疑惑才好让大家帮忙。

Protein synthesis begins when the gene encoding a protein is activated.
蛋白质合成，是自相应基因激活开始的。

The gene’s sequence of nucleotides is transcribed into a molecule of messenger RNA (mRNA), which reproduces the information contained in that sequence.
基因的次序传给MRNA。

Transported outside the nucleus to the cytoplasm, the mRNA is translated into the protein it encodes by an organelle known as a ribosome, which strings together amino acids in the order specified by the sequence of elements in the mRNA molecule.
从细胞核进入细胞质，MRNA经由R这种细胞器转化为蛋白质。R这个细胞器和氨基酸缠绕在一起，其缠绕次序由MRNA的次序来确定。

Since the amount of mRNA in a cell determines the amount of the corresponding protein, factors affecting the abundance of mRNA’s play a major part in the normal functioning of a cell by appropriately regulating protein synthesis.
由于MRNA的数量确定相应蛋白质的数量，影响MRNA数量的因素就很重要了。

For example, an excess of certain proteins can cause cells to proliferate abnormally and become cancerous; a lack of the protein insulin results in diabetes.
例如，某种蛋白质超量可导致细胞非正常扩散并癌变；缺乏胰岛素蛋白质则导致糖尿病。

Biologists once assumed that the variable rates at which cells synthesize different mRNA’s determine the quantities of mRNA’s and their corresponding proteins in a cell.
生物学家曾认为细胞合成MRNA的不同速率决定了量。

However, recent investigations have shown that the concentrations of most mRNA’s correlate best, not with their synthesis rate, but rather with the equally variable rates at which cells degrade the different mRNA’s in their cytoplasm.
但，近期研究表明，不是合成速度，而是分解速度更为重要。

If a cell degrades both a rapidly and a slowly synthesized mRNA slowly, both mRNA’s will accumulate to high levels.
如果分解慢，快速合成和慢速合成的都将达到高水平。

An important example of this phenomenon is the development of red blood cells from their unspecialized parent cells in bone marrow (bone marrow: n. 骨髓).
一个重要的例子是，红血球在骨髓种的成长。

For red blood cells to accumulate sufficient concentrations of hemoglobin (hemoglobin: n.血色素) (which transports oxygen) to carry out their main function, the cells’ parent cells must simultaneously produce more of the constituent proteins of hemoglobin and less of most other proteins.
为了红血球积累足够的血色素，母细胞必须同时产出较多的血色素和较少的其他蛋白质。

To do this, the parent cells halt synthesis of non-hemoglobin mRNA’s in the nucleus and rapidly degrade copies of the non-hemoglobin mRNA’s remaining in the cytoplasm.
为此，母细胞中断细胞核中非血色素MRNA的合成并加速细胞质中对其的分解。

Halting synthesis of mRNA alone would not affect the quantities of proteins synthesized by the mRNA’s still existing in the cytoplasm.
仅中止细胞核中的合成是无效的。

Biologists now believe that most cells can regulate protein production most efficiently by varying both mRNA synthesis and degradation, as developing red cells do, rather than by just varying one or the other.
所以，要双管齐下。

谢谢斑竹花了这么多的时间来解释我这个令人头晕的问题。下面是我不明白的一些问题，恳请斑竹再次帮忙

第５题，最后一段不都说了要双管齐下，为什么答案选Ａ“only degradaton:?估计我定位错了

另外两题已经从斑竹的翻译中看明白了，多谢。

5.     To begin to control a disease caused by a protein deficiency, the passage suggests that a promising experimental treatment would be to administer a drug that would reduce

如何控制蛋白质缺乏症？我们不妨自己先想想。
从文章来看，应该是减慢MRNA的分解速度(A选项所示)，或同时再加快其合成，所以A对。only the degradation rate for the mRNA of the protein involved
B反，错。only the synthesis rate for the mRNA of the protein involved
C部分反，错。both the synthesis and degradation rates for the mRNA of the protein involved
无关，错。the incidence of errors in the transcription of mRNA’s from genetic nucleotide sequences

多谢斑竹耐心解答，我忽略了Ｃ中的部分反，现在明白了。

问一下版主

第8题的C如何解释？

C本身说的道理应该没错吧？

是不是，C说的太明显了？不能叫做sugguestion?

还是，文章要问explanation，而C只能说明题干所说情况的发展结果，不能作为这个情况的解释，也就是原因。

不过总觉得D答案有点缺陷，如果说The mRNA’s for both proteins are being degraded at a low rate and being synthesized at a high rate in that type of cell才比较舒服。

我认为是“文章要问explanation，而C只能说明题干所说情况的发展结果，不能作为这个情况的解释，也就是原因。”Ｃ并不是在解释原因

如红色部分考虑的话，不是引入了文章并没有表述的专业知识了吗？

文章说了，an excess of certain proteins can cause cells to proliferate abnormally and become cancerous; a lack of the protein insulin results in diabetes

而我认为C说由于这些蛋白质偏高可能导致癌变，这个本身没错，只是文不对题，不能回到问题。如小猫妹妹所言

喔，我想再说明一下：首先，我所说的“其实，C描述的是比较恐怖的事情，因为正常组织中的某种蛋白质是常常位于高水平的。例如饭后胰岛素量大，但显然不能说可能癌变。”的确不是文章中所反应的内容，这只是我的补充说明，是为了说明，离开本文考虑一下，C很怪异。

而C的错误根源在于，文章中是说certain，而问题中没有certain这个限定,所以C就存在将各种蛋白质全包括的问题，所以就不对了。