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They can be from embryos or reprogrammed from adult tissues. Each team's models vary in the techniques used and how complete they are, he said, with some mirroring not just the embryo but the very beginnings of the placenta and yolk sac, too.įor these types of models, scientists use a kind of stem cell that is capable of developing into many different types of cells or tissues in the body. Real human embryos can be extremely hard to see at that stage because they burrow into the uterus. While previous models mimicked pre-embryos, Hyun said the latest ones model an embryo after it has implanted in the uterus. Other scientists in Israel and China published studies on their work earlier this month that have not yet been reviewed by peers. Teams with researchers from the United States and England shared their work in two studies published Tuesday in the journal Nature. Several groups are working on the research. Using models also avoids the controversy of using real embryos in research, he said. 'They're complete enough to give you a picture of what may be happening in the embryo during pregnancy, but they're not so complete that you could actually use them for reproduction,' said Insoo Hyun, an ethicist and director of life sciences at Boston's Museum of Science.

These models are made from stem cells, not egg and sperm, and can't grow into babies. Scientists have created embryo models to help study the mysteries of early human development, the medical problems that happen before birth and why many pregnancies fail.

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