Polly and Molly facts for kids

Polly and Molly (born in 1997) were two special sheep. They were the first mammals to be successfully cloned from an adult body cell AND to have genes from another species (making them transgenic animals) at the same time! This is different from Dolly the Sheep, who was also cloned from an adult body cell, but her genes weren't changed. Polly and Molly, just like Dolly, were created at the Roslin Institute in Edinburgh, Scotland.

Polly and Molly: Special Cloned Sheep

Polly and Molly were very important in the world of science. They showed that scientists could not only clone animals but also add new genes to them. This was a big step forward!

What Makes Polly and Molly Special?

The scientists who created Polly and Molly used a method similar to the one used for Dolly the Sheep. However, they added a new gene into the cells before cloning them. This new gene was for a special protein found in humans. The goal was to see if animals could be used to make medicines for people.

The human protein they chose was called factor IX. This protein helps blood clot. People who don't have enough of it suffer from a bleeding disorder called haemophilia B. Scientists hoped that sheep like Polly and Molly could produce this protein in their milk, making it easier and cheaper to get medicine for patients.

How Were They Made?

Before Polly and Molly, the main way to add new genes to animals was by injecting DNA directly into a fertilized egg. But this method didn't always work well. Only a few animals would get the new gene, and it was hard to control how much of the protein they would make. This made it a very expensive and often unsuccessful process.

In mice, scientists could use special stem cells to add new genes more precisely. But this method wasn't possible for larger animals like sheep.

The creation of Dolly the Sheep showed that scientists could clone sheep from different types of adult body cells. Polly and Molly took this idea a step further. Scientists first grew adult body cells in the lab. Then, they added the new human gene to these cells. They selected the cells that successfully took in the new gene.

Next, the nucleus (which contains the DNA) from these special cells was put into an empty egg cell. This process is called nuclear transfer. These new cells then developed into embryos, which were placed into a mother sheep. This led to the birth of several lambs, and two of them were named Polly and Molly. They were healthy and carried the new human gene.

Why Was This Important?

The new gene inserted into Polly and Molly was designed to make the human clotting factor IX protein in their milk. This protein is vital for blood clotting. People with haemophilia B need regular treatments with factor IX.

Making this protein in the milk of livestock, a process called pharming, could provide a much cheaper source of this medicine. It would also be safer than getting it from human blood, which can sometimes carry risks of infection. Polly and Molly proved that this amazing idea could actually work!

See also

In Spanish: Oveja Polly para niños