Section 9.1 Manipulating DNA – Flashcards
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Restriction Enzyme
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enzyme that cuts DNA molecules when they identify specific nucleotide sequences
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Gel Electrophoresis
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method of separating various lengths of DNA strands by applying an electrical current to a gel
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Restriction Map
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diagram that shows the lengths of fragments between restriction sites in the strand of DNA
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Who had determined the structure of DNA?
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Watson and Crick
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What are used to sequence genes?
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artificial nucleotides
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What are used to study gene expression?
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artificial copies of genes
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What are used to change DNA sequences?
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chemical mutagens
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What are enzymes used for?
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often from bacteria, are used to cut and copy DNA
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Why would scientists want to cut DNA?
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A gene is a sequence of DNA nucleotides, and a chromosome is one long DNA molecule. A whole chromosome is too large for scientists to study a specific gene easily, so they had to find a way to get much smaller pieces of DNA.
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What defense does bacterial cells (and your cells) use to protect itself from infecting viruses?
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Bacteria produce enzymes that cut up DNA of the viruses
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What is a restriction site?
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The sequence of nucleotides that is identified and cut by a restriction enzyme
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Why are they called restriction enzymes?
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Because they restrict, or decrease, the effect of the virus on the bacterial cell
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What are "blunt ends"?
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fragements of DNA left over from the process of cutting DNA through restriction enzymes
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Between what lengths do restriction enzymes recognize nucleotide sequences?
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4 and 8 base pairs long
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How do restriction enzymes cut DNA?
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Some enzymes make cuts straight across while others are staggered.
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What are "sticky ends"?
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When restriction enzymes make staggered cuts that leave tails of free DNA bases on each side of the cut. The nucleotide tails of cut DNA strands are called ____ ____. They are like tiny pieces of velcro that are ready to hook on to their opposite sides.
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What will happen if two pieces of DNA with sticky ends and complementary base pairs come close to each other?
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The two segments of DNA will join by hydrogen bonding.
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What happens during gel electrophesis?
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A sample of DNA is loaded into a gel, which is like a thin slab of hard gelatin. A positive electrode is at one end of the gel. At the other end is a negative electrode. Because DNA has a negative charge, the fragments move towards the positive electrode , or the positively charged pole. The tiny pores running through the gel allow small molecules to move quickly. Larger molecules cannot easily move through the gel and travel more slowly. Therefore, the length of a DNA fragment can be estimated from the distance it travels through a gel in a certain period of time.
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What do the bands on a gel indicate?
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the lengths of DNA fragments
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How are restriction maps used to study mutations?
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First, a mutation may add or delete bases between restriction sites, which would change the lengths of DNA fragments on a gel. Second, a mutation may change a restriction site, and the DNA would not be cut in the same places.
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How are comparisons of restriction maps useful?
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It can help diagnose genetic diseases. A restriction map from a person's DNA can be compared with a restriction map from DNA that is known to be normal. If the maps differ , it is an indication that the person has inherited a disease-causing allele of the gene.
