First human clone? (Life News).
The ACT "clone" didn't grow beyond the size of six cells, smaller than the tip of a ballpoint pen. Still, some researchers think a successfully cloned human embryo is imminent. "People are saying they know how to do it," says Dr. Edward McCabe at UCLA's Mattel Children's Hospital. "It remains to be seen if they really can."
How do you clone a person? The process starts with a single human egg (female sex cell). A scientist extracts the egg's DNA--genetic material found in each of the body's billions of cells that serves as a blueprint for growth--and replaces it with the DNA of the person to be cloned (see diagram, top).
Normally, to create a human embryo, an egg must be fertilized (fused) with a sperm, or male sex cell. (For more on reproduction, see "Amazing Animal Babies" on page 8.) But cloned eggs don't need sperm. Dolly the sheep, the first cloned animal, has no biological father!
Instead of sperm, ACT scientists use a mix of chemicals and hormones (brain substances) to persuade the egg to divide into two identical daughter cells, then four, etc. If successful, after about five days of division, the cells form a blastocyst, a hollow sphere that houses stem cells--cells with the potential to form any of the body's 200 cell types, such as muscle or heart cells.
If cloning is perfected, a doctor might harvest stem cells and use them to grow replacement parts for faulty cells that cause deadly diseases such as Alzheimer's (memory disorder) or diabetes (blood sugar disorder).
But the process is far from easy: So far, 68 of 71 cloning eggs at ACT have died. Other researchers have had luck cloning animals, such as sheep, mice, and cattle, but no known cloned human cells have yet reached the blastocyst stage. Even more controversial are the ethical issues. At press time, Congress was hotly debating whether or not to allow human cloning at all.
THE CLONING TECHNIOUE
Advanced Cell Technology is the first company to announce that they've cloned a human embryo. Their ultimate goal, researchers say, is not to create a human being but to use stem cells found inside the embryo for life-saving medical research. Here's how cloning is done.
STEP 1: DNA (genetic information) is removed from cell center (nucleus).
STEP 2: DNA from another person's adult cell is injected into empty egg.
STEP 3: As if it had been fertilized (fused) by a sperm (male sex cell), egg begins to grow and divide to form an embryo.
STEP 4: Five days later, a blastocyst forms. The hollow ball of about 100 cells contains special cells (stem cells) capable of becoming any cell type in the body.
STEP 5: Scientists harvest stem cells for use in new medicines to treat diseases like diabetes, a blood sugar disorder.
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|Date:||Feb 25, 2002|
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