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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu DNA Identification The repeating sequences in noncoding DNA vary between individuals and thus can be used to identify an individual. Ch 9-1 & 9-2
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Steps in DNA Identification 1.Copying DNA –To identify a DNA sample, scientists isolate the DNA and copy it using the Polymerase Chain Reaction (PCR) –Millions of copies are made in just a few hours
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Polymerase Chain Reaction
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Steps in DNA Identification 2.Cutting DNA –The DNA is then cut into fragments using restriction enzymes –Restriction enzymes recognize and cut specific nucleotide sequences called a restriction site.
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Restriction Enzymes Cut DNA
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Steps in DNA Identification 3.Sorting DNA by Size –The fragments are separated by size using gel electrophoresis –A positive electrode is attached to one side of the gel (a thin slab of hard gelatin) –A negative electrode is attached to the other side –An electric current is sent through the gel and the DNA (which is slightly negative) moves towards the positive side
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Steps in DNA Identification 3.Sorting DNA by Size –There are pores in the gel for the DNA to move through –Large pieces of DNA stop sooner (closer to the negative end) –Small pieces of DNA move farther (closer to the positive end) –The resulting pattern of bands is called a DNA fingerprint –a Restriction map shows the lengths of the bands produced in the gel
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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Gel Electrophoresis
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