Somatic cell nuclear transfer

Scientists can make a twin cell.

First, they take an egg. They take out the tiny part that holds information. Next, they take a part from a body cell. They put that part into the empty egg.

Then, they use a tiny shock. This helps the egg start to grow. The egg can grow into a new living thing. It will be just like the body cell.

One famous animal was a sheep named Dolly. She was a big success for science. This work can help people who are sick. It is very neat!

Scientists use a special way to make clones. This way is called somatic cell nuclear transfer. A clone is a living thing that is a twin to another.

To start, scientists take an egg cell. They remove the nucleus. The nucleus is the tiny part that holds all the instructions for life. This leaves an empty egg. Next, they take a somatic cell from a body. This could be a skin cell or a liver cell. They put the nucleus from that body cell into the empty egg.

Then, they give the egg a tiny shock. This helps the egg start to grow. The egg becomes a blastocyst. A blastocyst is a very early stage of an embryo with about 100 cells.

This work can help sick people. Scientists can make stem cells from these embryos. Stem cells are special cells that can turn into any part of the body. This might help doctors fix damaged organs. In 1996, a sheep named Dolly became famous. She was the first mammal made this way from an adult cell.

Scientists use a special way to make clones. This is called somatic cell nuclear transfer, or SCNT. A clone is a living thing that is a twin to another. This method can be used for two main reasons. It can be used for reproductive cloning to make a new animal. It can also be used for therapeutic cloning to help doctors.

Therapeutic cloning focuses on making stem cells for medicine. These cells can help fix parts of the body that are broken. This is a very important tool for modern science.

To make a clone, scientists must follow a careful way it works. First, they take a female egg cell, also called an ovum. They must remove the egg's own nucleus, which holds its instructions. This leaves an empty egg cell. Next, they take a somatic cell from a body. A somatic cell is just a regular body cell like skin or fat.

Scientists put the nucleus from that body cell into the empty egg. They then give the egg a tiny shock to make it start dividing. The egg grows into a blastocyst, which is an early embryo with about 100 cells.

People have been studying this for a long time. In 1958, Sir John Gurdon cloned a frog called Xenopus laevis. He used light to remove the nucleus from the egg. Later, a very famous event happened in 1996. A sheep named Dolly was born using this technique. She was the first mammal cloned from an adult body cell.

In January 2018, scientists in Shanghai cloned two macaques named Zhong Zhong and Hua Hua. These were the first monkeys cloned from fetal nuclei.

There are many important numbers and places in this science. In the United States, labs at Harvard and the University of California San Francisco study this. In the United Kingdom, groups at the Roslin Institute do research too. Scientists once found that adding caffeine helped embryos grow better. In 2014, researchers used adult cells from people aged 35 and 75. They proved that the age of a cell does not stop it from being reprogrammed. This was a huge step for medical science.

This science connects to how our own bodies work. The stem cells made from SCNT can turn into many different types of tissue. For example, scientists used cells from a person with diabetes. They turned those cells into parts that make insulin. This could one day help people who are very sick. It is like having a toolkit to build new parts for a machine. Science helps us understand how to use these tiny building blocks to help life.

Somatic cell nuclear transfer, often called SCNT, is a laboratory strategy used to create a viable embryo. This process involves combining a body cell with an egg cell to produce a clone. A clone is an organism that has an identical genome to the original donor. Scientists use this technology for two main purposes: reproductive cloning and therapeutic cloning. Reproductive cloning aims to create a new, living organism. Therapeutic cloning focuses on regenerative medicine. In this approach, scientists create embryonic stem cells to study diseases or create new tissues.

The SCNT process requires two specific types of cells. The first is a female gamete, also known as an ovum or oocyte. The second is a somatic cell, which is any cell from a body, such as a skin, fat, or liver cell. To begin, scientists must perform enucleation. This means they remove the original genetic material from the egg cell, leaving it "deprogrammed." Once the egg is empty, a donor nucleus from a somatic cell is inserted into the egg's cytoplasm. The egg is then stimulated with an electric shock. This shock causes the egg to begin dividing. As the cell divides through mitosis, it eventually forms a blastocyst. A blastocyst is an early-stage embryo containing about 100 cells.

There are different ways to perform this transfer in a lab. Many scientists use micromanipulators, which are expensive, high-precision machines. Using a pipette, a scientist makes a small opening in the zona pellucida, the outer layer of the egg. They suck out the original nucleus and then inject the new donor nucleus. Another method uses electric energy to fuse a somatic cell directly with an empty egg. In 2001, Indian scientists described "handmade cloning." This method does not require a micromanipulator. Instead, they use a chemical called phytohaemagglutinin to glue the egg to the donor cell before using electricity to fuse them.

History shows that SCNT has been studied for many decades. While Dolly the sheep is the most famous example, she was not the first animal cloned. In 1958, Sir John Gurdon cloned a frog species called Xenopus laevis. He used ultra-violet irradiation to disable the egg's pronucleus during enucleation. In 1996, Dolly became the first mammal successfully cloned from an adult somatic cell. More recently, in January 2018, a team in Shanghai announced they had cloned two female crab-eating macaques. These monkeys, named Zhong Zhong and Hua Hua, were cloned from fetal nuclei.

Research into human SCNT has faced many technical challenges. In early experiments, human cells often failed to develop past the eight-cell stage. Scientists believe the somatic nucleus sometimes fails to turn on the embryonic genes needed for growth. However, a research group from the Oregon Health & Science University found a solution. They used oocytes in metaphase II, or MII, of the cell cycle. These specific eggs contain cytoplasmic factors that help reprogram the donor nucleus. By adding caffeine during the process, they improved the formation of the blastocyst.

Significant breakthroughs have occurred regarding the age of donor cells. In 2014, an international team proved that age does not prevent successful reprogramming. They successfully grew stem cells using adult cells from two different donors, aged 35 and 75. This was important because scientists previously thought age-related changes might hinder the process. This discovery opened more doors for using adult cells in medical research. It showed that the biological clock of a cell does not stop it from becoming a pluripotent stem cell.

The ultimate goal of therapeutic SCNT is to create patient-specific cells. These are pluripotent stem cells, which means they can turn into any tissue in the body. If a scientist uses a patient's own cells, the resulting tissues will be a perfect genetic match. This helps avoid immune system rejection during transplants. For example, the New York Stem Cell Foundation used cells from a type 1 diabetic. They successfully turned these cells into insulin-producing cells. This work demonstrates how SCNT can be used to create replacement therapies for serious diseases.