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Bell Ringer:

Bell Ringer:. Have your vocabulary numbered on the side of your desk! 1-How are base pairing rules related to Chargaff ’ s research on DNA? 2-In a sample of yeast DNA 31.5% of the bases are adenine. Predict the approximate percentages of C, G, and T.

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Bell Ringer:

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  1. Bell Ringer: • Have your vocabulary numbered on the side of your desk! • 1-How are base pairing rules related to Chargaff’s research on DNA? • 2-In a sample of yeast DNA 31.5% of the bases are adenine. Predict the approximate percentages of C, G, and T. • 3-How many rings are there on each base pair?

  2. KEY CONCEPT DNA replication copies the genetic information of a cell.

  3. new strand original strand Two molecules of DNA REPLICATION = DNA making DNA

  4. Replication copies the genetic information. • A single strand of DNA serves as a template for a new strand. • The rules of base pairing directreplication. • DNA is replicated during theS (synthesis) stage of thecell cycle. • Each body cell gets acomplete set ofidentical DNA.

  5. nucleotide The DNA molecule unzips in both directions. Proteins carry out the process of replication. • DNA serves only as a template in a three step process.

  6. Enzymes and other proteins do the actual work of replication. • DNA polymerases are proteins (enzymes) that form bonds between nucleotides during replication. • DNA poly = tells us it makes DNA polymers • Ases = tells us its an enzyme

  7. nucleotide The DNA molecule unzips in both directions. • Step ONE • Enzymes unzip the double helix an numerous places along the chromosome. (these places are called origins of replication) This means the hydrogen bonds connecting base pairs are broken, the original molecule separates, and the bases on each strand are exposed. This process proceeds in two directions at one time.

  8. nucleotide new strand DNA polymerase • Step TWO: • Free-floating nucleotides pair, one by one, with the bases on the template strands as they are exposed. DNA polymerases bond the nucleotides together to form new strands that are complementary to each template strand.

  9. new strand original strand Two molecules of DNA • STEP THREE • Two new molecules of DNA are formed, each with an original strand and a newly formed strand. DNA replication is semiconservative. (one old and one new strand)

  10. There are many origins of replication in eukaryotic chromosomes. Replication is fast and accurate. • DNA replication starts at many points in eukaryotic chromosomes. The replication “bubbles grow larger as replication progresses. • DNA polymerases can find and correct errors.

  11. DNA replication takes about eight hours in human cells. If there were only one origin the process would take about a hundred times longer.

  12. Question • In step 1 how does the DNA unzip?

  13. Question • In step 2, how do the new strands compare with the template strands?

  14. Question • What is the result of DNA replication?

  15. Question • Why is it important for the cell to correct any errors that occur during replication?

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