Cloning: Threat or Opportunity?
design | feature | impact | potential | transfer
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Think Scientifically
Think Scientifically
The students in Mr. Seemy’s class are arguing about the potential impact of cloning on society. Suddenly, Chris says, “Wait a minute. I’m not sure I even understand what cloning is. I imagine some sort of bizarre copy machine, or a giant test tube or fish tank with copies of people and animals growing in it, but I have a feeling that’s just science fiction.”
Miranda says, “It has something to do with DNA, the molecule that controls what physical features get transferred from parents to their children. Usually a baby gets a mix of its parents’ DNA, but cloning somehow involves copying just one individual’s DNA to make another individual. But I don’t know how that’s actually done.”
“The first mammal that scientists cloned was a sheep, back in 1996,” says Mr. Seemy. “They named the cloned sheep Dolly, and she was probably the world’s most famous sheep! Why don’t you two do a little research on how Dolly was cloned?”
Chris and Miranda did some research and put together the following short description of the cloning process used to produce Dolly. This is still the general approach used for cloning animals.
On the left is Miranda and Chris’s simplified five-step summary of how to clone an animal. But the images on the right, designed to illustrate the process, are all mixed up. See if you can match each step to its correct illustration. The first one is done for you.
Step 1: Take an egg cell from a female sheep and remove the nucleus from the egg. (The nucleus is where a cell’s DNA is.)
Step 2: Take a non-reproductive cell (not an egg or sperm cell) from the sheep you want to clone. Transfer the nucleus from that cell to the nucleus-free egg.
Step 3: Give the egg cell a small electric shock to make it start dividing. As it divides, it grows into an embryo, which is an unborn organism in the earliest stages of development.
Step 4: Put the embryo into another sheep who will be the surrogate (substitute) mother.
Step 5: The surrogate mother sheep gives birth to a sheep that is a genetic copy—a clone—of the sheep that provided the DNA from its non-reproductive cell.
Discussion Question:
How would you design a cloning experiment to produce a male sheep? A female sheep?
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