History of Cloning: Reading Comprehension

A Quiz on The History of Cloning

Read the text about the history of cloning and choose the correct answer to each question.

History of Cloning

Cloning is not new. Experiments with frogs and toads date back to the 1970s. And experiments involving plants and animal embryos have been performed for years. But experiments involving human beings had never been tried or thought possible, until "Dolly." Her birth shocked the scientific community and has spurred discussion about the possibility of human clones. Dr. Lee Silver, a molecular biologist at Princeton University, is optimistic that "human cloning will occur." Some scientists argue that a safe technology could be developed in the future. This has led to discussion about whether human cloning should even be legally possible.
Numerous events have occurred since the birth of "Dolly" that have only complicated this Controversial issue over human cloning.
When the scientists cloned "Dolly", the cloning technique "somatic cell nuclear transfer" was used . The process is as follows: DNA coming from a single cell taken from a motheregg, is fused with a mammary cell. The fused cell then develops into an embryo, which is implanted in a "surrogate" sheep. The embryo grows into a lamb, which is genetically identical to the donor sheep.
Though it has been touted as a success, this cloning procedure is not perfect. It took more than 277 attempts before "Dolly" was created as a health viable lamb. Human cloning is far more complicated, with greater risks and potentials for error. As a result, scientists fear that applying this technique to humans might lead to malformations or diseases in the human clone.
True human cloning would require taking a somatic cell, as opposed to a reproductive cell such as an egg or sperm cell, from a person and removing its nucleus. The DNA of the somatic cell would be transferred to an enucleated egg cell. But this is not currently possible because the somatic cells are specialized and there are many genes that have been "turned off" that we do not know how to turn back "on".

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