Zhong Zhong and Hua Hua facts for kids

Zhong Zhong (born November 27, 2017) and Hua Hua (born December 5, 2017) are two female crab-eating macaques. They are special because they are the first primates (a group of mammals that includes monkeys, apes, and humans) to be successfully cloned using a method called somatic cell nuclear transfer (SCNT). This is the same technique that created Dolly the sheep in 1996.

Unlike earlier attempts to clone monkeys, the scientists used cells from a monkey fetus (an unborn baby monkey) instead of very early embryo cells. Zhong Zhong and Hua Hua were born from two different surrogate mothers at the Institute of Neuroscience in Shanghai, China.

What is Cloning?

Cloning means making an exact copy of something. In biology, it means creating a new organism that is genetically identical to another. Imagine making a perfect twin, but not in the usual way!

Early Cloning Successes

Scientists have been able to clone animals for a while. The most famous cloned animal is Dolly the sheep, born in 1996. She was the first mammal cloned from an adult cell. Since Dolly, scientists have cloned over 20 different kinds of mammals. These include animals like cows, cats, dogs, and horses.

Challenges with Primates

Cloning primates, like monkeys, was much harder. For a long time, no cloned primate pregnancy lasted more than 80 days. The main problem was getting the DNA from the donor cell to "reset" properly. This resetting is needed for the DNA to guide the growth of a new embryo.

Before Zhong Zhong and Hua Hua, another monkey named Tetra was cloned in 1999. Tetra was a rhesus macaque. However, Tetra was made using a simpler method called "embryo splitting." This is like creating identical twins naturally, but in a lab. The SCNT method used for Zhong Zhong and Hua Hua is much more complex.

Cloned Monkeys for Health Studies

In January 2019, scientists in China announced they had cloned five more monkeys. These monkeys were also "gene-edited," meaning their DNA was changed in specific ways. These cloned, gene-edited monkeys were created to help scientists study serious human diseases. This research helps us understand how diseases work and how to find new treatments.

How Zhong Zhong and Hua Hua Were Cloned

Zhong Zhong and Hua Hua were created by scientists at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai. The research was led by Qiang Sun and Mu-ming Poo.

The SCNT Process

• Step 1: Getting the DNA. Scientists took tiny cells called fibroblasts from an aborted fetal monkey. Fibroblasts are common cells found in connective tissue.
• Step 2: Preparing the Egg. They took unfertilized egg cells from other monkeys. They carefully removed the nucleus (which contains the DNA) from each egg cell.
• Step 3: Inserting the DNA. The nucleus from the fetal fibroblast cell was then put into the empty egg cell.
• Step 4: Reprogramming. This was the most important and difficult step. The scientists used special chemicals and enzymes. These helped to "reset" the DNA from the fibroblast cell. This made the DNA act like it was from a brand new embryo, ready to grow into a whole new animal. This "reprogramming" was the key breakthrough that allowed them to clone primates successfully.
• Step 5: Growing the Embryo. The newly created cells started to divide and grow, forming early embryos.
• Step 6: Surrogate Mothers. The scientists placed 21 of these embryos into different surrogate mother monkeys. Six of these monkeys became pregnant. Out of these six pregnancies, two resulted in live births: Zhong Zhong and Hua Hua.

The monkeys were named Zhong Zhong and Hua Hua as a reference to Zhonghua, which is a Chinese name for China.

Success Rate

Even though they succeeded, the process was still very difficult. For comparison, the team that cloned Dolly the sheep in 1996 had to try 277 times to get just one lamb. The methods used for Zhong Zhong and Hua Hua can likely be improved in the future to increase the success rate.

The scientists also tried to clone monkeys using cells from adult donors. This is even harder. They tried with 42 surrogate mothers, and 22 became pregnant. However, only two baby macaques were born, and they sadly died soon after birth. This shows how challenging it is to clone from adult cells.

Why is This Important?

The birth of Zhong Zhong and Hua Hua is a big step in science.

Research and Medicine

One of the main reasons for cloning animals like these monkeys is for scientific research. Genetically identical monkeys are very useful for studying diseases. Because they are exact copies, scientists can be sure that any differences they see in their studies are due to the disease or treatment, not differences in the animals themselves.

These cloned monkeys could help scientists learn more about serious human diseases. For example, they could be used to study brain diseases like Parkinson's disease and Alzheimer's disease. They could also help in understanding other conditions like atherosclerosis, which affects blood vessels.

Ethical Questions

The cloning of primates also brings up important questions about ethics. Some people wonder if this means human cloning could be next. Scientists involved in the research, like Mu-ming Poo, have stated clearly that there are no plans to clone humans. The research is focused on understanding biology and finding cures for diseases.

See also

In Spanish: Zhong Zhong y Hua Hua para niños

• List of animals that have been cloned