Lauren Allen Monday at 6 Due April 2, 2007 Animal Development Pre-lab
Briefly explain cloning There are several ways to clone: 1. Make multiple copies of a DNA sequence 2. To clone an animal (like Dolly) from a clone cell. Cloning DNA sequences To clone you need a set of enzymes called restriction endonucleases. They are enzymes that are able to fragment DNA at certain restriction sites. These endonucleases cut the DNA which have sticky ends and used to be then inserted into bacterial plasmids and then cloned when the bacteria reproduced. From these, you can make a clone library. Cloning Animals When Dolly, the sheep was cloned, they took a mammary cell out of one of her "parents" and grew it in a solution that held up the cell cycle and a nucleus was removed from an egg cell with a micropipette. The mammary cell was then inserted inside the covering of an egg cell. Electric shock opens cell membranes and triggers cell division. The embryo then begins to develop in vitro and is implanted into the surrogate mother. The pregnancy was five months long and a lamb that was genetically identical to the sheep from which the mammary cell was extracted from. Why Cloning Fails "Normal development depends on precise genomic imprinting. This chemical reprogramming of the DNA...takes months for sperm and years for eggs." During cloning the reprogramming must take minutes. The reprogramming job is not done nearly as well because of the time difference. "Human cloning will not be practical until scientists figure out how to reprogram a donor nucleus, as occurs in the DNA of sperm or eggs in our bodies." (Raven 7th Edition Biology)
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