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最小的自然数是1。
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同类题1

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    A new study suggests that the timing of a wound affects the speed at which it heals(愈合). Wounds suffered during the day heal around 60 percent faster than those at night.

    The study showed how the body's circadian rhythm(昼夜节律) controlled the healing of wounds____ It tells our bodies when to wake up, eat and sleep in a cycle—a series of activities that repeat themselves day after day____

    In the study, researchers found that skin cells moved faster to repair wounds suffered during the day. Their findings were published in the journal Science Transnational Medicine.

    The researchers examined cells, mice, and burn injury databases____Night-time burns—burns suffered between 8 o'clock at night and 8 o' clock the next morning—were 95percent healed after an average of 28 days.

    But after an average of 17 days, daytime burns-burns suffered between 8 o'clock in the morning and 8 o'clock at night—were 95 percent healed____

    Wounds are very costly to treat____In Britain's National Health Services, for example, such services cost around $6.56 billion per year. Experts say the high costs result, in part, from a lack of drugs that speed up the closure of wounds.

A. Each cycle lasts about 24 hours.

B. The circadian rhythm is like a clock or timer.

C. Specifically their investigation found the following information:

D. The new study's findings could help scientists develop better drugs.

E. In other words, nigh-time injuries took an average of 11days longer to heal

F. Worldwide, billions of dollars are spent every year on wound-treatment services.

G. That's what a group of researchers from a university in Canada recently published.

同类题2

2012年诺贝尔生理学或医学奖授予约翰•伯特兰•戈登和山中伸弥,以表彰他们在“体细胞重编程技术”领域做出的革命性贡献.请回答下列问题:

(1)1962年约翰•伯特兰•戈登通过实验把蝌蚪肠上皮细胞的细胞核移植进入去核的卵细胞中,成功培育出“克隆青蛙”.此实验说明已分化的动物体细胞的____ 具有全能性.更多的实验证明,到目前还不能用类似____ 技术(克隆植物的方法)获得克隆动物.

(2)所谓“体细胞重编程技术”是将高度分化的体细胞重新诱导回早期干细胞状态,即获得诱导多能干(iPS)细胞.山中伸弥于2006年把4个关键基因通过逆转录病毒转入小鼠的成纤维细胞,使其转变成iPS细胞.在该技术中,逆转录病毒是这4个关键基因的____ ,在其协助下4个基因进入成纤维细胞,并整合到染色体的____ 上.

(3)培养iPS细胞时,培养液需要特别加入的天然成分是____ ,同时iPS细胞需置于____ 培养箱中培养.

(4)iPS细胞可诱导分化成各种细胞类型以应用于临床研究.现用胰高血糖素基因片段做探针,对iPS细胞分化成的甲、乙、丙细胞进行检测,结果如下表:

用探针检测细胞的DNA

用探针检测细胞的RNA

iPS细胞

甲细胞

乙细胞

丙细胞

iPS细胞

甲细胞

乙细胞

丙细胞

+

+

+

+

+

注:“+”表示能检测到,“﹣”表示不能检测到

得到此检测结果采用的是____ 技术;结果表明iPS细胞通过____ 定向分化为乙细胞.