Cloning of embryos has been used in mice experiments since the late 1970's, and in animal breeding since the late 1980's. The procedure splits a single fertilized ovum into two or more clones, each of which is then implanted into the womb of a receptive female.
However, research into cloning of human embryos has been restricted in the United States and in some other countries. Pro-life groups which oppose free access to abortion have had considerable political power. They were able to have all human embryo research banned by the Regan and Bush Presidencies during most of the 1980's and into the early 1990's. During the first few days of President Clinton's presidency, the ban on public funding of human embryo and fetal research was lifted.
We may not know the individual or team who first performed cloning of human embryos. The methods used have been understood for many years and actually used to clone embryos in cattle and sheep. It is likely that someone had successfully used the method on a human embryo in secret. The first publicly announced human cloning was done by Robert J. Stillman and his team at the George Washington Medical Center in Washington D.C. They took 17 genetically flawed human embryos which would have died within days no matter how they were treated. They were derived from an ovum that had been fertilized by two sperm. This resulted in an extra set of chromosomes which doomed the ovum's future. None could have developed into a fetus. These ovum were successfully split in 1994-OCT, each producing one or more clones. The main motive of the experiment seems to have been to trigger public debate on the ethics of human cloning.
Dr. Steven Muller headed a panel in the US whose mandate was to produce preliminary cloning guidelines. These would be used by the Federal National Institutes of Health to decide which cloning research to fund. The panel recommended that studies be normally limited to the use of preexisting, spare embryos - those that developed during in vitro fertilization procedures that had been performed to assist couples in conceiving. Generally about 20 or 24 ova are fertilized during these procedures. Only three or four are implanted in the woman. The extra zygotes are either discarded or frozen for possible future use. New embryos would only be prepared and used if needed for "compelling research." They further recommended that any studies be normally terminated within 14 days of conception. Some experiments might be authorized to continue until the 18th day, but no further. At that gestational age, neural tube closure begins; this is the start of the development of a nervous system. They recommended that certain procedures be banned, including implanting human embryos in other species, implanting cloned embryos into humans, the transfer of a nucleus from one embryo to another, and the use of embryos for sex selection.
However, research into cloning of human embryos has been restricted in the United States and in some other countries. Pro-life groups which oppose free access to abortion have had considerable political power. They were able to have all human embryo research banned by the Regan and Bush Presidencies during most of the 1980's and into the early 1990's. During the first few days of President Clinton's presidency, the ban on public funding of human embryo and fetal research was lifted.
We may not know the individual or team who first performed cloning of human embryos. The methods used have been understood for many years and actually used to clone embryos in cattle and sheep. It is likely that someone had successfully used the method on a human embryo in secret. The first publicly announced human cloning was done by Robert J. Stillman and his team at the George Washington Medical Center in Washington D.C. They took 17 genetically flawed human embryos which would have died within days no matter how they were treated. They were derived from an ovum that had been fertilized by two sperm. This resulted in an extra set of chromosomes which doomed the ovum's future. None could have developed into a fetus. These ovum were successfully split in 1994-OCT, each producing one or more clones. The main motive of the experiment seems to have been to trigger public debate on the ethics of human cloning.
Dr. Steven Muller headed a panel in the US whose mandate was to produce preliminary cloning guidelines. These would be used by the Federal National Institutes of Health to decide which cloning research to fund. The panel recommended that studies be normally limited to the use of preexisting, spare embryos - those that developed during in vitro fertilization procedures that had been performed to assist couples in conceiving. Generally about 20 or 24 ova are fertilized during these procedures. Only three or four are implanted in the woman. The extra zygotes are either discarded or frozen for possible future use. New embryos would only be prepared and used if needed for "compelling research." They further recommended that any studies be normally terminated within 14 days of conception. Some experiments might be authorized to continue until the 18th day, but no further. At that gestational age, neural tube closure begins; this is the start of the development of a nervous system. They recommended that certain procedures be banned, including implanting human embryos in other species, implanting cloned embryos into humans, the transfer of a nucleus from one embryo to another, and the use of embryos for sex selection.
Labels: Embryo cloning
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