VOA慢速英语2020--圣地亚哥动物园克隆濒危的马

At the San Diego Zoo, in Southern California, little Kurt looks and acts like any other baby horse. He likes to play, pushes against anything that gets in his way, and runs to his mother for milk when he is hungry.

But the 2-month-old differs from every other baby horse in the world in a major way: Kurt is a clone. He was created in a laboratory.

Scientists used cells taken from a male Przewalski's horse in 1980. The cells had been frozen¹ for the last forty years. The scientists also took an egg from a female horse of a different breed. Then, they removed the egg's nucleus² and replaced it with the cells from the Przewalski's horse.

The resulting embryo³ was placed in the womb of another female horse for development. She gave birth to Kurt on August 6.

Scientists have cloned more than twenty other kinds of animals, including dogs, cats, pigs, cows and mice. In 2018, researchers in China created monkeys for the first time using the same cloning methods that produced the first cloned animal, Dolly the sheep, in 1996.

San Diego Zoo officials say Kurt is the first cloned Przewalski's horse, a rare and endangered breed.

The zoo sees Kurt's birth as a major step in efforts to reestablish the population of the Przewalski's horse, also known as the Asiatic Wild Horse or Mongolian Wild Horse. The small, thickset horses are believed to have disappeared from the wild. About 2,000 live in zoos and wildlife centers.

Bob Wiese is chief life sciences officer at San Diego Zoo Global, which operates the zoo. He said that Kurt is expected to be one of the most genetically⁵ important individuals of his breed.

"We are hopeful that he will bring back genetic⁴ variation important for the future of the Przewalski's horse population," he added.

Kurt was named for Dr. Kurt Benirschke, who created the Frozen Zoo, a research and collection center at the San Diego Zoo. It provided the scientists with the Przewalski's horse cells used to make Kurt.

The zoo worked jointly⁶ with the California conservation group Revive⁷ & Restore and the Texas-based company ViaGen Equine in creating Kurt. He was born at a veterinary facility in Texas. He is expected to continue to live there with his mother for another year.

Later, Kurt will move to the San Diego Zoo to live with other Przewalski's horses. Zoo officials hope Kurt will someday become a father himself.

Przewalski's horses take their official name from Russian explorer Nikolai Przewalski, who found a skull⁸ and skin of one and shared it with a Russian museum.

At one time the horses lived throughout Europe and Asia, says the Smithsonian's National Zoo and Biology Conservation Institute. Growing populations of humans and farm animals pushed them out of Europe and east into Asia. Outside of zoos, they exist today only in special protected areas of Mongolia, China, and Kazakhstan.

The Smithsonian says Przewalski's horses are the only true wild horses left in the world. It says that wild horse groups in North America and Australia are not truly wild because their ancestors were horses that escaped human owners.

Words in This Story

breed – n. a group of animals or plants thought to be related to one or more common ancestors

variation - n. the act or process of being different

1 frozen   

adj.冻结的，冰冻的

参考例句：

• He was frozen to death on a snowing night.在一个风雪的晚上，他被冻死了。
• The weather is cold and the ground is frozen.天寒地冻。

2 nucleus   

n.核，核心，原子核

参考例句：

• These young people formed the nucleus of the club.这些年轻人成了俱乐部的核心。
• These councils would form the nucleus of a future regime.这些委员会将成为一个未来政权的核心。

3 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

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 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物

6 jointly   

ad.联合地，共同地

参考例句：

• Tenants are jointly and severally liable for payment of the rent. 租金由承租人共同且分别承担。
• She owns the house jointly with her husband. 她和丈夫共同拥有这所房子。

7 revive   

v.（使）复苏，（使）重振活力，恢复生机，复兴

参考例句：

• These flowers will revive in water.这些花在水中会再活。
• They managed to revive the injured driver with cardiac massage.他们通过心脏按压使受伤的司机苏醒了过来。

8 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。