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Sickle¹ cell disease is a blood disorder² due to a single genetic⁴ mutation⁵. It remains⁶ in populations because the mutation has a flip⁷ side—it helps to protect against malaria⁸. Now another mutation has been shown to afford similar protection. Deficiency in the enzyme⁹ glucose-6-phosphate-dehydrogenase, known as G6PD deficiency, leads to anemia¹⁰ and jaundice. The condition affects more than 400 million people.

Scientists had thought that the prevalence of the deficiency might also be linked to protection against malaria, but they weren’t able to find a connection in Africa. Now a study in Asia shows how the gene³ for G6PD-deficiency can indeed help. It appeared in the December 11th edition of the journal Science. The deficiency is particularly common in Myanmar and Thailand. So researchers spent eight years studying the Karen people in Thailand, who live near the Myanmar border. They showed that the mutation definitely reduces the number of malaria-causing Plasmodium vivax parasites¹¹, lessening¹² the severity of the disease.

This protective effect has kept the genetic condition active in the population. Researchers hope that the good side of the mutation can be exploited to develop new and better ways to fight malaria.

—Cynthia Graber

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1 sickle
n.镰刀
参考例句：
The gardener was swishing off the tops of weeds with a sickle.园丁正在用镰刀嗖嗖地割掉杂草的顶端。 There is a picture of the sickle on the flag. 旗帜上有镰刀的图案。

2 disorder
n.紊乱，混乱；骚动，骚乱；疾病，失调
参考例句：
When returning back,he discovered the room to be in disorder.回家后，他发现屋子里乱七八糟。 It contained a vast number of letters in great disorder.里面七零八落地装着许多信件。

3 gene
n.遗传因子，基因
参考例句：
A single gene may have many effects.单一基因可能具有很多种效应。 The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

4 genetic
adj.遗传的，遗传学的
参考例句：
It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。 Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

5 mutation
n.变化，变异，转变
参考例句：
People who have this mutation need less sleep than others.有这种突变的人需要的睡眠比其他人少。 So far the discussion has centered entirely around mutation in the strict sense.到目前为止，严格来讲，讨论完全集中于围绕突变问题上。

6 remains
n.剩余物，残留物；遗体，遗迹
参考例句：
He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。 The remains of the meal were fed to the dog.残羹剩饭喂狗了。

7 flip
vt.快速翻动；轻抛；轻拍；n.轻抛；adj.轻浮的
参考例句：
I had a quick flip through the book and it looked very interesting.我很快翻阅了一下那本书，看来似乎很有趣。 Let's flip a coin to see who pays the bill.咱们来抛硬币决定谁付钱。

8 malaria
n.疟疾
参考例句：
He had frequent attacks of malaria.他常患疟疾。 Malaria is a kind of serious malady.疟疾是一种严重的疾病。

9 enzyme
n.酵素，酶
参考例句：
Above a certain temperature,the enzyme molecule will become unfolded.超过一定温度，酶分子将会展开。 An enzyme that dissolves the fibrin of blood clots.能溶解血凝块中的纤维的酶。

10 anemia
n.贫血，贫血症
参考例句：
The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 I was put on iron tablets for my anemia.我曾因贫血吃补铁药片。

11 parasites
寄生物( parasite的名词复数 )；靠他人为生的人；诸虫
参考例句：
These symptoms may be referable to virus infection rather than parasites. 这些症状也许是由病毒感染引起的，而与寄生虫无关。 Kangaroos harbor a vast range of parasites. 袋鼠身上有各种各样的寄生虫。

12 lessening
减轻，减少，变小
参考例句：
So however much he earned, she spent it, her demands growing and lessening with his income. 祥子挣多少，她花多少，她的要求随着他的钱涨落。来自汉英文学 - 骆驼祥子 The talks have resulted in a lessening of suspicion. 谈话消减了彼此的怀疑。