Zhong Zhong and Hua Hua facts for kids

Zhong Zhong (Chinese: 中中; pinyin: Zhōng Zhōng, born November 27, 2017) and Hua Hua (Chinese: 华华; pinyin: Huá Huá, born December 5, 2017) are two identical crab-eating macaques, a type of monkey. They were created using a special cloning method called somatic cell nuclear transfer (SCNT). This is the same technique that was used to create Dolly the sheep in 1996. Zhong Zhong and Hua Hua are the first primates (a group that includes monkeys, apes, and humans) to be cloned using this specific method. Unlike earlier attempts to clone monkeys, the cells used for Zhong Zhong and Hua Hua came from a developing baby monkey, not from very early embryo cells. These two monkeys were born from two different surrogate mothers at the Institute of Neuroscience in Shanghai, China.

How Cloning Works

Since Dolly the sheep was cloned in 1996, scientists have successfully cloned 23 different kinds of mammals. These include animals like cows, cats, dogs, horses, and rats. However, cloning primates using the SCNT method had never worked before. No primate pregnancy had lasted longer than 80 days. The main challenge was making sure the new cell nucleus could properly guide the growth of the embryo.

Another monkey named Tetra was born in 1999. She was a female rhesus macaque and was also a clone. However, Tetra was created using a different, simpler method called "embryo splitting". This is like creating identical twins artificially. The SCNT method used for Zhong Zhong and Hua Hua is much more complex.

In 2019, Chinese scientists also created five identical cloned monkeys. They used the same SCNT method as for Zhong Zhong and Hua Hua. These monkeys were also "gene-edited," meaning their genes were changed using a tool called CRISPR-Cas9. These cloned monkeys were made to help study different medical diseases.

The Cloning Process

Scientists from the Institute of Neuroscience in Shanghai, China, led by Qiang Sun and Mu-ming Poo, created Zhong Zhong and Hua Hua. Here's how they did it:

• They took cells called fibroblasts from a developing baby monkey.
• They removed the nucleus (which contains the DNA) from these fibroblast cells.
• They then took egg cells from other monkeys and removed their original nuclei.
• The nucleus from the fibroblast cell was then put into the empty egg cell.
• The team used two special chemicals to "reset" the memory of the transferred nucleus. This was a very important step. It helped the nucleus act like it was in a new egg cell, which was the main problem in earlier primate cloning attempts.
• Next, 21 of these new egg cells were placed into surrogate mother monkeys.
• This resulted in six pregnancies, and two of them led to the birth of Zhong Zhong and Hua Hua.

The monkeys were named Zhong Zhong and Hua Hua as a nod to Zhonghua (Chinese: 中华), which is a Chinese name for China. Even though the success rate was low, scientists believe they can make the process better in the future. For comparison, the team that cloned Dolly the sheep in 1996 tried 277 times and only got one lamb.

The scientists also tried to clone monkeys using cells from adult monkeys. This is much harder. They put these cells into 42 surrogate mothers, which led to 22 pregnancies. However, only two baby monkeys were born, and they sadly died soon after birth.

Why Cloning Matters

According to Mu-ming Poo, a lead scientist, the most important reason for cloning these monkeys is for animal experiments. These cloned monkeys are genetically identical, meaning they are exactly alike. This makes them very useful for studying diseases. For example, they can help scientists learn more about diseases like Parkinson's disease and Alzheimer's disease.

The birth of these two cloned primates also brought up some questions about ethics. Some people wondered if this meant that human cloning would be next. Mu-ming Poo said that while it might be possible, scientists are not planning to clone humans. He stated, "There's absolutely no plan to do anything on humans."

See also

In Spanish: Zhong Zhong y Hua Hua para niños

• List of animals that have been cloned