1. Slide 1 of 21 Copyright Pearson Prentice Hall 12-2 Chromosomes and DNA Replication 12–2 Chromosomes and DNA Replication

2. 12–2 Chromosomes and DNA Replication Slide 2 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes In prokaryotic cells, DNA is located in the cytoplasm. Most prokaryotes have a single DNA molecule containing nearly all of the cell’s genetic information.

3. 12–2 Chromosomes and DNA Replication Slide 3 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Chromosome E. Coli Bacterium Bases on the Chromosomes

4. 12–2 Chromosomes and DNA Replication Slide 4 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Many eukaryotes have 1000 times the amount of DNA as prokaryotes. Eukaryotic DNA is located in the cell nucleus inside chromosomes. The number of chromosomes varies widely from one species to the next.

5. 12–2 Chromosomes and DNA Replication Slide 5 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Chromosome Structure Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin. Chromatin consists of DNA tightly coiled around proteins called histones. DNA and histone molecules form nucleosomes. Nucleosomes pack together, forming a thick fiber.

6. 12–2 Chromosomes and DNA Replication Slide 6 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Eukaryotic Chromosome Structure Chromosome Supercoils Nucleosome DNA double helix Histones Coils

7. 12–2 Chromosomes and DNA Replication Slide 7 of 21 Copyright Pearson Prentice Hall DNA Replication What happens during DNA replication?

8. 12–2 Chromosomes and DNA Replication Slide 8 of 21 Copyright Pearson Prentice Hall DNA Replication Duplicating DNA Before a cell divides, it duplicates its DNA in a process called replication. Replication ensures that each resulting cell will have a complete set of DNA.

9. 12–2 Chromosomes and DNA Replication Slide 9 of 21 Copyright Pearson Prentice Hall DNA Replication During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

10. 12–2 Chromosomes and DNA Replication Slide 10 of 21 Copyright Pearson Prentice Hall DNA Replication Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth

11. 12–2 Chromosomes and DNA Replication Slide 11 of 21 Copyright Pearson Prentice Hall DNA Replication How Replication Occurs DNA replication is carried out by enzymes that “unzip” a molecule of DNA. Hydrogen bonds between base pairs are broken and the two strands of DNA unwind.

12. 12–2 Chromosomes and DNA Replication Slide 12 of 21 Copyright Pearson Prentice Hall DNA Replication The principal enzyme involved in DNA replication is DNA polymerase. DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.

13. Slide 13 of 21 Copyright Pearson Prentice Hall 12–2 In prokaryotic cells, DNA is found in the a.cytoplasm. b.nucleus. c.ribosome. d.cell membrane.

14. Slide 14 of 21 Copyright Pearson Prentice Hall 12–2 The first step in DNA replication is a.producing two new strands. b.separating the strands. c.producing DNA polymerase. d.correctly pairing bases.

15. Slide 15 of 21 Copyright Pearson Prentice Hall 12–2 A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand? a.GCGAATTCG b.CGCTTAAGC c.TATCCGGAT d.GATGGCCAG Go to Section 12-3 Go to Section 12-3

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