2019年12月15日 13:15:22|来源:国际在线|编辑:预约优惠
Don:Heres a simple demonstration you can do with cool implications.唐:这是一个你可以做的具有很酷含义的简单演示。Find a large object that is brightly colored--lets make it a green door.找一个色鲜艳的大物件—让我们使它摇身一变成为一道绿色门。Stand with that door to your side but dont look directly at it; you want it to be in your peripheral vision.站在那扇门身边,但不要直视,你要想它是在你的周边视觉中。Now, without shifting your gaze, examine the door in the edge of your field of vision.现在,不用转移你的目光,仔细审视在你视野边缘的这扇门。What color is it? Answer? Its still green.它是什么颜色的?回答?它仍然是绿色的。Yael:Its still green? What kind of experiment is that?雅艾尔:它仍然是绿色的吗?这个实验到底想说明什么?I thought you were going to say something happens to the color.我以为你会说颜色发生了某些变化。Don:Thats exactly right!唐:完全正确!The color stays green, which means something has happened-- because nothing in your peripheral vision should have any color at all.之所以仍然是绿色,这意味着发生了一些事情—因为在你的周边视觉里应该应该没有任何颜色。Yael:Nothing in your peripheral vision should have any color? Why not?雅艾尔:在你的周边视觉内应该没有任何颜色?为什么没有呢?Don:Because color is what we perceive when light of a particular frequency meets cones-special cells in your retina.唐:因为颜色是特定频率光线投射到视网膜锥细胞上我们的感知。But the light being reflected off the door is only landing on the outside edge of your retina.但被反射到门的光只是在你的视网膜外边缘。And there are almost no cones on the edges.而且在边缘几乎没有视锥细胞。Everything we see roughly seventy-five degrees away from the point were fixed on should be black and white.从这一个固定的点大约七十五度我们看到的一切事物都应该是黑白两色。Yael:Thats fascinating! But why is the door still green?雅艾尔:太神奇了!但为什么门还是绿色的?Don:Presumably the door remains green because vision isnt a simple matter of retinal cells.唐:大概门仍然是绿色的是因为视觉不是简单的视网膜细胞。All the data your eyes send is interpreted by the brain.你眼中的所有数据发送给大脑解读。Your brain knows that the door is green, so it supplies information that isnt really there to keep the image stable.你的大脑知道门是绿色的,所以它提供信息,并不是真的在那里保持图像稳定。This is just one of the many ways your brain saves time and energy by making reasonably safe assumptions about the world around you.这只是你的大脑通过对你周围环境合理安全的假设节省时间和精力的其中一种方式。 201311/264414

During the last ice age, rapid swings in temperature occurred within decades or less, meaning populations of organisms had to adjust quickly to new environments or face extinction.在最后一个冰河世纪中,温度在数十年甚至更短的时间内迅速变化,这意味着生物种群不得不快速调整来适应新的环境,否则等待它们的只有种族灭绝。Scientists knew there wasnt time for the genetic code to mutate within individuals and sp throughout large populations. So, how did animals respond? Ancient bison preserved in the Canadian arctic have given scientists a clue.科学家知道那时基因编码没有时间在个体中产生变异并在种群中大范围地传播。那么,动物们是如何应对的?在加拿大北极圈内保留的古代野牛标本给科学家们提供了一些线索。When genes were first identified, scientists thought they were hard wired. One gene made one protein and was unalterable. Today we know the story is much more complex. Part of that complexity is known as epigenetics, a process by which genes are modified by environmental factors.第一次识别古代野牛的基因时,科学家们认为它们是固定相连的。一个基因对应一个蛋白质并且无法改变。如今我们知道故事远没有那么简单。其中一部分复杂性来自表观遗传学,它是基因通过环境因素发生改变的过程。The genetic code stays the same, but certain molecules attach to the code to prevent specific genes from working or to change how they are expressed. Other molecules can affect the chromosome and alter the way the DNA unwinds, affecting how genes work.基因密码保持不变,但是某个为阻止某个特定基因工作或变更的密码附属分子发生了变化。而其它分子可以通过影响染色体并改变DNA解旋的方式来影响基因的表达。Extracting DNAScientists examining twenty six thousand year old bison bones looked for evidence of epigenetic changes in extracted DNA. They analyzed the genetic code for a particular kind of epigenetic change called DNA methylation. They not only found methylations, they found them in locations where they occur in modern cattle. That suggested they werent due to DNA degradation, but were true epigenetic changes.DNA提取科学家检查了已有26000年历史的古代野牛的骨头,试 图在提取的DNA中找到表观遗传变异的据。他们分析了一种特定种类的表观变化(被称为DNA甲基化)的基因密码。他们不但找到了甲基化,而且发现它们跟 现代牛群体内发现的位置是一样的。这表明它们不是发生了DNA退化,而是真正的表观遗传变异。This is just the first step in solving the ice age adaptation puzzle. Scientists plan to gather more DNA samples from animals that lived before and after the dramatic climatic shifts. That way theyll have genetic snapshots to compare. If comparisons prove successful, the next step will be to determine exactly how the epigenetic alterations changed the gene expression.这仅仅是解决冰河世纪适应谜团的第一步。科学家计划在气候剧烈变化前后生存过的动物身上收集更多的DNA样本。如此一来,他们就有更多的基因用来比较。如果比较的结果明是之前的推断是正确的,那么下一步是确定表观变化是如何影响基因表达的。 /201305/240484

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