科学60秒:是什么让猛犸象熬过冰河时期？
来源：沪江听写酷
2011-04-13 09:21
文章较难，大家听写填空即可~
A couple million years ago, mammoths migrated north from Africa to colonize Eurasia. Sometime around then a massive ice age ___1___—and it was stay warm or die. So their tails and heat-shedding ears shrunk, and they grew thick coats of oily fur.
But if you're out in the cold all day you also need some biochemical adjustments. Hemoglobin is the protein in red blood cells that delivers oxygen to your tissues. And it doesn't ___2___ oxygen well at low temperatures; it just ___3___ it more tightly. So mammoths solved that problem by evolving hemoglobin that releases oxygen more easily in the cold. That’s according to a study published in the journal Nature Genetics.
Researchers got the DNA that codes for hemoglobin from a 43,000-year-old mammoth. Then they used E. coli bacteria to produce actual mammoth hemoglobin. They compared mammoth hemoglobin to that of their living cousins, Asian elephants, at 37, 25 and 10 degrees Celsius. Due to just a few ___4___, mammoth hemoglobin can release oxygen more readily at cold temperatures. Which was just the thing to help mammoths ___5___.
A couple million years ago, mammoths migrated north from Africa to colonize Eurasia. Sometime around then a massive ice age ___1___—and it was stay warm or die. So their tails and heat-shedding ears shrunk, and they grew thick coats of oily fur.
But if you're out in the cold all day you also need some biochemical adjustments. Hemoglobin is the protein in red blood cells that delivers oxygen to your tissues. And it doesn't ___2___ oxygen well at low temperatures; it just ___3___ it more tightly. So mammoths solved that problem by evolving hemoglobin that releases oxygen more easily in the cold. That’s according to a study published in the journal Nature Genetics.
Researchers got the DNA that codes for hemoglobin from a 43,000-year-old mammoth. Then they used E. coli bacteria to produce actual mammoth hemoglobin. They compared mammoth hemoglobin to that of their living cousins, Asian elephants, at 37, 25 and 10 degrees Celsius. Due to just a few ___4___, mammoth hemoglobin can release oxygen more readily at cold temperatures. Which was just the thing to help mammoths ___5___.
kicked in
off-load
clings to
key structural changes
keep their cool
数百万年前，猛犸象从非洲出发，进军欧亚大陆。就在那时，冰河时期来临了，在那种情况下，猛犸象要么想办法保暖，要么就只有冻死的份儿了。为适应环境，它们的尾巴和用来散热的大耳朵退化了，毛皮则变得又厚又多脂。
你要是整天呆在寒冷的环境中，也会需要点生化调节。血红蛋白是人体内负责输送氧气的红细胞中的蛋白质。但是，在低温环境下，血红蛋白与氧黏着越发紧密，因此不能很好地卸载氧。当初，猛犸象是如何攻克这一难题的呢？它们的血红蛋白进化了——变得更容易在寒冷环境中卸载氧。（参见《自然-遗传学》）
研究人员从一头43000岁的猛犸象标本中获取了其血红蛋白DNA，然后用大肠杆菌培养新的血红蛋白。之后又将该血红蛋白和与它们形似的亚洲象的血红蛋白作对比，观察它们在37℃、25℃和10℃环境条件下的差异。结果发现，正是由于一些关键的构造性变异，猛犸象的血红蛋白能够更好地在低温环境下卸载氧，借此，猛犸象得以在冰河时期潇洒生存~
