WHICH OF THE SENTENCES IN THE FIRST PARAGRAPH■ WHICH OF THE FOLLOWI...

3. Which of the sentences in the first paragraph

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Which of the following is least relevant to themain idea of the passage?is least relevant to the main idea of theparagraph?Where to Find Misplaced Sentencesa. Heat is used to cause the division.You will usually be directed to a particular paragraph.b. The DNA is divided down the center likeunzipping a zipper.If the first sentence states the main idea of the para-c. The goal is to discover the sequence of basesgraph, it is unlikely to be the misplaced sentence.in the DNA.Check all others.d.If this is a mitochondrial DNA fragment, thesequence will be like the person’s mother andSample Passage and Questionmaternal relatives.The goal is to discover the sequence of bases in thee. Only one half (side of the zipper) is used.DNA. If this is a mitochondrial DNA fragment, theAnswermaternal relatives. The DNA is divided down theThe passage describes the process of reading DNA. Thecenter like unzipping a zipper. Heat is used to causesecond sentence has nothing to do with the process. Itthe division. Only one half (side of the zipper) isshould have been placed in a paragraph that discussedused. The sequence of bases will be discovered byvocabulary. The answer is d.recreating the other half.Preparing for Organization(This passage will be continued in the next section,QuestionsReading 3.)To further prepare for the test, as you read any book,magazine, or paper, you might want to take note of dif-ferent ways paragraphs are structured and how sen-tences follow in a logical sequence.

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C B E S T M I N I - C O U R S E

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R e a d i n g 3 : U n m a s k i n g

will show the sequence of bases. Bases A and T

t h e M a i n I d e a

always bind to each other. Bases C and G alwaysbind to each other. The idea is to put one-half of aMain idea questions can be put in three categories. TheDNA strand in a test tube with some free bases andan enzyme that causes the free bases to attach to thefirst asks for a simple sentence or title that includes thehalf strand—rezipping the zipper. Modified basesmain topic of the passage. The second asks questionsare also added so that the location of that base onabout the author and what the author had in mind.Then there are those that ask for a paraphrase of all thethe “zipper” can be marked. In this way, themain ideas in the passage.sequence of bases can be discovered. Each test tubecontains thousands of copies of the saved half of thePure and SimpleDNA strand, and a radioactive primer which willSimple main idea questions take a variety of forms:attach at the start location of every strand so that alloperations start at the same place on every strand.

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What is the main idea of the passage?Also included are DNA polymerase, which is an

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The best title for this passage would be . . .enzyme that acts as a “glue” to attach the free bases

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What is the theme of the passage?to the half DNA strand, and all four bases, which are

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The central thought of the passage is . . .free and unattached. There is also a modified base—each test tube has a different base which has beenHow to Find Main Idea Answers in themodified to act as a marker during reconstruction.PassageAt the end of the process, thousands of recon-To answer main idea questions, you sometimes do notstructed strands will be in each test tube. Some ofhave to read the whole passage. Often the main idea isthese strands will be complete, but some of themstated at the beginning or end of the passage. Some-will have been terminated by a modified base sotimes you can glean the main idea by paying attentionthey will be shorter. All of them will have the sameto the topic sentences of each paragraph of the passage.sequence of bases but will terminate at differentpositions where A is found. The reason that some ofthe strands did not terminate at base A is that a nor-This passage continues the passage on DNA that youmal instead of a modified base A attached at somebegan in the previous section.of the base A locations. There is a test tube for eachbase. Therefore, there are reconstructed strandswhich terminate with C in the test tube with mod-ified C bases, strands which terminate with G in thetest tube with modified G bases, and strands whichterminate with T in the test tube with modified Tbases. The four test tubes are used in order to tell thedifference between bases since the strands and basesall look alike. However, the same test can be done inone test tube if fluorescent dyes are used to tag theThe next goal is to use the half of the DNA whichmodified bases.was saved to reconstruct the other half. This processa large number of students living in housing proj-