How Dolly the Sheep was cloned

Summary

This animation describes the groundbreaking process by which scientists at the Roslin Institute cloned Dolly, the first mammal cloned from an adult cell. The process involved taking udder cells from a Dorset ewe (sheep 1), deprogramming them to restore their potential, and fusing them with an enucleated egg from a Scottish ewe (sheep 2). The fertilized egg was then implanted in a surrogate ewe (sheep 3). After 277 attempts, Dolly was born on July 5, 1996, genetically identical to sheep 1. She lived until February 2003 before being put down due to a lung disease.

Takeaways

• 😀 The Roslin Institute scientists successfully cloned Dolly, the first mammal to be cloned from adult cells.
• 😀 The cloning process involved taking cells from the udder of Sheep 1, the animal to be cloned.
• 😀 The cells from Sheep 1 were cultured and deprogrammed to become totipotent, meaning they could form any cell type.
• 😀 An egg was removed from Sheep 2, a black-faced female Scottish ewe, and its nucleus was removed (enucleated) to eliminate Sheep 2's DNA.
• 😀 The deprogrammed cells from Sheep 1 were fused with the enucleated egg from Sheep 2, making the egg genetically identical to Sheep 1.
• 😀 After fusion, the egg was stimulated to begin cell division, simulating fertilization.
• 😀 The growing cell cluster was implanted into the womb of a third sheep (Sheep 3) for gestation.
• 😀 A total of 277 attempts were made to achieve a successful cloning, with only one successful birth—Dolly.
• 😀 Dolly was born on July 5th, 1996, via cesarean section, and was found to be genetically identical to Sheep 1.
• 😀 Dolly lived until February 14th, 2003, when she was euthanized due to a progressive lung disease, living a relatively short life for a sheep.
• 😀 Dolly's creation demonstrated that adult cells could be reprogrammed to revert to a totipotent state, significantly advancing the science of cloning and genetics.

Q & A

What was the main goal of the Roslin Institute scientists in this study?

The main goal was to create Dolly, the first mammal to be cloned from adult somatic cells, specifically from a sheep's udder cells.

Why were the parent sheep labeled as Sheep 1 and Sheep 2?

Sheep 1 was the donor sheep whose udder cells were used for cloning, while Sheep 2 provided the egg for the cloning process. Sheep 2's black face was used to distinguish it from Sheep 1.

What was the significance of deprogramming the cells from Sheep 1?

Deprogramming the cells allowed them to regain totipotency, meaning they could develop into any type of cell needed for the future clone, rather than simply becoming more udder cells.

What role did Sheep 2 play in the cloning process?

Sheep 2 provided the egg, which was enucleated (its nucleus removed) so that no genetic material from Sheep 2 would contribute to the cloning process.

How was the process of cloning similar to human fertilization?

The process involved removing the nucleus from Sheep 2's egg and fusing it with a cell from Sheep 1's udder, mimicking the way a sperm fertilizes an egg, but with both DNA copies coming from Sheep 1.

What happens after the egg is fused with the somatic cell?

Chemical factors in the egg stimulate cell division, leading to the formation of an embryo, which is then implanted into the uterus of a third sheep for gestation.

How many attempts were made before Dolly was successfully cloned?

A total of 277 attempts were made to fuse the adult cells with the enucleated eggs, with only one successful attempt resulting in Dolly.

What method was used to deliver Dolly?

Dolly was delivered by cesarean section after a 21-day gestation period in Sheep 3.

What was unique about Dolly compared to other sheep?

Dolly was genetically identical to Sheep 1, as she was cloned from Sheep 1's udder cells, making her the first mammal cloned from an adult somatic cell.

What caused Dolly's death?

Dolly was euthanized on February 14, 2003, after suffering from a progressive lung disease.