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 Related Pages: Cloning Clones |
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GENETIC ENGINEERING: "There are many techniques, or tools, that are available to the scientist allowing her to conduct her cloning experiment. Just as you would use some different tools to build a table than when you want to fix a car, the scientist will choose the tools that make the most sense for what she wants to achieve. "Let's look at some of the tools that scientists can use. "One of the most basic tools, and the first to be used, is what scientists call 'molecular scissors'. These are a whole bunch of enzymes which are naturally made by various bacteria. Each one will cut a DNA strand at a specific nucleotide sequence. You can think of it as smart scissors that recognize a certain string of letters and snips every time it sees that string. Let's make our own smart scissors and see what happens to the sentence: MARY HAD A LITTLE LAMB "First, let's make smart scissors that cut on the left side of the letter A.
"The A-smart scissors produces 5 pieces of our sentence. Now, let's make smart scissors that cut in the middle of LITT.
"With our LITT-smart scissors, we only have two pieces of our sentence. Now, let's make smart scissors that cut to the right of HEARD.
"Our HEARD-smart scissors don't cut our sentence at all, because there is no sequence of letters HEARD in our sentence. "So, the scientist's molecular scissors are like our smart scissors in that they cut when they see a certain series of nucleotide-'letters' and that there are many different types of molecular scissors available. "Why do scientists want to cut the DNA at all? Well, sometimes they don't, they use all the DNA from a cell. But, at other times, they only want one gene. Then they must cut it out. If they know the DNA sequence of the gene, the scientist can pick molecular scissors that do not cut inside the gene. If they know the DNA sequence on either side of the gene, they can pick molecular scissors that cut near the gene, but not in it. Let's do that with our smart scissors. MARY HAD A LITTLE LAMB "If we want to cut out the gene 'LITTLE', which of our smart scissors would we use? We would use the A-smart scissors, because they cut near the gene 'LITTLE' but not in it. The LITT-smart scissors cut in the gene 'LITTLE', and the HEARD-smart scissors cut far from the gene. "Other tools that scientists have provide ways of getting the gene into a new cell's DNA. The first thing the scientist must do is open small holes in the new cell's membrane. They can do this by putting the new cell in a certain solution that causes the holes to form, or they can expose the new cell to electric current that also opens up holes. The gene then floats into the cell and floats around until it comes near the cell's DNA. The cell's own enzymes, seeing a gene floating around will link it up to the rest of the DNA. Now the scientist's gene is ready to function. "Let's put our gene 'LITTLE' into a different sentence. We will have to say 'Abra-Ca-Dabra' for our experiment to work. Ready?
"Nicely done! Now, the scientist would make her new cell grow and divide to make a cell line and she's got herself a clone with the gene she wants in all the cells' DNA. Scientists do this type of cloning to get bacteria or yeast to produce human insulin -- that's ME! I'm the gene that codes for insulin! The insulin is then used by diabetics for their medicine. "But what of the scientist that wants to put all of one cell's DNA into another cell? They can do that with large cells that have a nucleus. With a very slender pipette, the scientist removes the nucleus from the target cell and throws that nucleus away. Then they take the nucleus from the donor cell and put it into the target cell.
"Now, if the target cell is a fertilized egg, it can be put into an animal's uterus and will grow into a baby. That's what the Scottish scientists did to clone the sheep, Dolly. All of Dolly's cells have exactly the same DNA as the donor sheep cell that was used. But, when Dolly grows up and mates with a ram, her babies will have a mixture of her and the ram's DNA; the babies will not be identical to Dolly. To make more clones of Dolly, the scientists need to keep doing this nucleus transfer. "Well, that's all the basics of DNA, cells, RNA, protein, and cloning. If you want to find more cool sites to visit on the internet, Polly, Chloe, RayNA and I have some suggestions for you."
GENETIC ENGINEERING:
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