1. Chromosomes and DNA Replication http://highered.mcgraw- hill.com/sites/0072943696/student_view0/chapter3/animation__dna_replication_ _quiz_1_.html

2. 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.

3. DNA and Chromosomes Eukaryotic Chromosome Structure Chromosome Supercoils Nucleosome DNA double helix Histones Coils

4. 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.

5. DNA and Chromosomes Chromosome E. Coli Bacterium Bases on the Chromosomes

6. The Components and Structure of DNA I The Components and Structure of DNA DNA is made up of nucleotides. A nucleotide is a monomer of nucleic acids made up of: Deoxyribose – 5-carbon SugarDeoxyribose – 5-carbon Sugar Phosphate GroupPhosphate Group Nitrogenous BaseNitrogenous Base

7. The Components and Structure of DNA There are four kinds of bases in in DNA: adenineadenine guanineguanine cytosinecytosine thyminethymine

8. The Components and Structure of DNA Chargaff's Rules Erwin Chargaff discovered that: –The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA. –The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA.

9. 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.

10. The Components and Structure of DNA DNA Double Helix

11. The Components and Structure of DNA Watson and Crick discovered that hydrogen bonds can form only between certain base pairs—adenine and thymine, and guanine and cytosine. This principle is called “the base pairing rule”.

12. DNA Replication II Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing. In most prokaryotes, DNA replication begins at a single point and continues in two directions.

13. Copyright Pearson Prentice Hall DNA Replication In eukaryotic chromosomes, DNA replication occurs at hundreds of places. Replication proceeds in both directions until each chromosome is completely copied. The sites where separation and replication occur are called replication forks.

14. Duplicating (replicating) 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.

15. During DNA replication: 1.The DNA molecule separates into two strands. Each strand of the double helix of DNA serves as a template for the new strand. This is carried out by an enzyme, DNA helicase, that “unzips” a molecule of DNA at the Hydrogen bonds between base pairs and the two strands of DNA unwind.

17. DNA Replication 2. It produces two new complementary strands following the rules of base pairing as each nucleotide matches the exposed base on each side of the ladder, DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.

18. DNA Replication Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth

19. DNA Replication

20. END OF SECTION http://www.youtube.com/watch?v=zd DkiRw1PdU http://content.dnalc.org/content/c15/ 15509/replication_basic.mp4 http://www.youtube.com/watch?v=zd DkiRw1PdU