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科学快讯
来源:中国科学报      作者:美国科学促进会      时间:2015-04-06 19:05      关键词:科学快讯


将突变传播给邻近染色体

研究人员已经知道如何用一种相对新的基因编辑技术将只有一个突变基因的某生物转变成有两个突变基因的生物。在二倍体生物(即那些有两套染色体的生物)中, 基因变异株并排排列,每股染色体上各有一个变异株。如果一个基因变异株为正常而另外一个发生突变(这种情况被称作杂合突变),该生物常常不会显示突变的性 状。然而,研究人员常常想研究该突变体的性状。如果突变的扩散能带来好处,他们甚至可能想将突变在一群生物体中扩散,就像能重新给蚊子的基因组编程以消灭 疟疾一样。利用最近研发出的CRISPR/Cas9基因组编辑方法,Valentino Gantz和Ethan Bier推出了一个系统,它能将一种杂合突变转变成一种纯合突变,在后者中的两个基因都发生突变。他们的工作涉及用一种突变的MCR成分注射到正常(或称 野生型)的蝇类胚胎中。MCR用最初的突变基因变异株来同样地使相对染色体上的基因突变。作者们在果蝇中证明,97%的时候,MCR突变会从其源染色体扩 散至其伙伴染色体,它甚至会发生在生殖细胞(即那些代代相传的细胞)中。作者们指出,MCR技术可能会在基础科学、医药和农业中有广泛的应用,尽管其应用 也会有风险。他们同意应该对这种技术的负责任使用进行讨论的呼吁。

超新星是产生宇宙星尘的工厂吗

有关星尘可在一颗超新星的炽热余波中存留下来的证据表明,超新星可能是在最早的星系中产生星尘的占主导地位的机制。多年来,研究人员一直在尝试对在极其遥 远的星系中存在大量星尘作出解释;这些星系看上去像是它们处于早期的宇宙之中。但在此之前,人们一直不清楚由某超新星产生的星尘是否能挺住该超新星的逆向 冲击,后者是由快速扩张的超新星喷射物与相对较冷、致密的环绕恒星的介质之间的热压差引起的。Ryan Lau和同事用来自装在一架波音747SP飞机上的被称作SOFIA的空中观测台的红外观测来分析在一颗超新星残留物中的星尘;该超新星残留物位于我们银 河系的中央附近。这一被称作SgrA East的超新星残留物大约有1万年之久,研究人员提出,大约有7%-20%的其最初的星尘块挺过了其冲击。这些发现意味着,有比预期更多的星尘挺过了早 期宇宙的情况。且在宇宙最古老星系中所见的星尘可能来自超新星。

从液浴中快速持续地进行3D打印

研究人员想出了一种从某种液浴中长出细小固形物的方法。研究人员说,这些固形物可从液体中被抽出,其速度之快会让目前的三维(3D)打印速度相形见绌,它 能让部件在几分钟内而不是多个小时内被打印出来。尽管现在有可能使用相对小而且低成本的机器来进行3D打印,但这仍然是一个相当慢的过程:对打印的每一层 次而言都会涉及数个步骤,其中包括对物体进行重新定位并添加下一层的打印材料。用这样的方法,某个高度只有几厘米的物体会花几个小时来构建。John Tumbleston等人现在设计了一种更快的方法来打印三维物体。其过程的关键是在源材料液浴与被打印的固形部件间创建一个含氧的“死区”。在这个死区 内不会发生固化;相反,固形物的向上移动能不断地将液体从浴液中抽出。该物体接着会通过在该死区上的液体固化而被打印出。该技术或被用来打印软质弹性材 料、陶瓷及像组织等生物材料。

(本栏目文章由美国科学促进会独家提供)


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