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DNA Replication p. 295-299

DNA Replication p. 295-299. Step 1: Special enzymes unwind & “unzip” the DNA molecule into 2 strands. Step 2: The strands separate so each strand can be a template for making another strand.

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DNA Replication p. 295-299

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  1. DNA Replicationp. 295-299

  2. Step 1:Special enzymes unwind & “unzip” the DNA molecule into 2 strands.

  3. Step 2:The strands separate so each strand can be a template for making another strand.

  4. Step 3:2 new strands are formed using the rules of base pairing (A-T, C-G). Nucleotides are added in opposite directions.

  5. Step 4:Each of the 2 new DNA molecules re-wind.

  6. Enzymes Involved • Helicase • Unzips the two strands and holds them apart during replication • DNA Polymerase • Links the nucleotides to form the new strands of DNA • Proofreads each new strand of DNA

  7. Original strand New strand DNA polymerase Growth DNA polymerase Growth Nitrogenous bases New strand Original strand DNA Replication

  8. ComparingDNA Replication Cytoplasm Nucleus S phase S phase So daughter cells have the same genetic information Start at 1 point, moves in both directions Starts at 100’s of points, moves in both directions.

  9. Review • Why is DNA replication needed? • When does DNA replication occur? • How many strands are there in a DNA molecule? • What are the three structures that make up a nucleotide? • What is the importance of base pairing? • When during DNA replication are enzymes used? • DNA replication results in ____ DNA molecules, each with one ______ strand and one _______ strand. • What happens to the two new DNA molecules?

  10. Answers to Review • So each daughter cell gets the same genetic info. • S phase of interphase • Two strands • A sugar (deoxyribose), a phosphate group, & a nitrogenous base (A, T, G, or C) • So each strand can be used as a template • HelicaseUnzips strands & holds them apart DNA polymerase  Joins new nucleotides & proofreads • DNA replication results in two DNA molecules, each with one old strand and one new strand. • They separate during anaphase and enter two different cells.

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