Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

0801 dna rep


Published on

DNA Replication NOt

Published in: Technology
  • Be the first to comment

  • Be the first to like this

0801 dna rep

  1. 1.
  2. 2. Cell Division Cycle <ul><li>New cells are produced by division of existing cells </li></ul><ul><li>If many new cells are needed, cells go through a cycle of events again and again </li></ul><ul><li>This is called the cell division cycle </li></ul>
  3. 3. <ul><li>The longest phase in this cycle is interphase </li></ul><ul><li>During interphase the cell carries out many biochemical reactions and grows larger , increase numbers of organelles </li></ul><ul><li>The DNA molecules in the chromosomes are not coiled up (chromatin) and the genes on them can be transcribed to allow protein synthesis </li></ul><ul><li>If the cell is going to divide again, the DNA is all replicated </li></ul><ul><li>These and other processes make interphase a very active period for a cell </li></ul>DNA replication chromosomes condense cell grows and develops
  4. 4. Interphase: DNA Replication <ul><li>DNA replication is a way of copying DNA to produce new molecules with the same base sequence </li></ul>
  5. 5. antiparallel strands of DNA
  6. 6. Base Pairing during Replication <ul><li>Each old strand serves as the template for complementary new strand </li></ul>
  7. 7. <ul><li>Semiconservative model of DNA replication </li></ul><ul><ul><li>Each molecule formed by replication consists of one new strand and one old strand conserved from the parent DNA molecule thus each new DNA molecule is a combination of one parent strand and one newly replicated strand </li></ul></ul>
  8. 8.
  9. 9.
  10. 10. Replication begins at multiple sites at the same time E. Coli
  11. 11. Continuous and Discontinuous Assembly <ul><li>Strands can only be assembled continuously toward the replication fork in the 5’ to 3’ direction </li></ul><ul><li>The discontinuous side must be assembled in chunks called Okazaki fragments </li></ul>
  12. 12.
  13. 13. 1. 2. 3. 4. 5. 6. Summary of DNA replication:
  14. 14. <ul><li>Step 1. Helicase enzyme unwinds the parent double helix. Hydrogen bonds are broken and strands are separated </li></ul><ul><li>Step 2. Binding proteins stabilize unwound DNA </li></ul><ul><li>Step 3. Single strands act as templates for new strands. Free nucleotides are present in large numbers around the replication fork. DNA polymerase synthesizes the continuous 5’  3’ leading strand by forming hydrogen bonds between the complementary bases </li></ul><ul><li>Steps 4. and 5. Primase enzyme and another DNA polymerase enzyme synthesize the lagging strand fragments (Okazaki fragments) </li></ul><ul><li>Step 6. DNA ligase joins the Okazaki fragments together. The daughter DNA molecules each rewind into a double helix </li></ul>DNA Replication Summary
  15. 15. Enzyme Roles and Names
  16. 16. Where does the energy come from for DNA Replication? <ul><li>Deoxynucleoside triphosphates (dNTP) </li></ul><ul><li>Base + deoxyribose + THREE phosphates </li></ul><ul><ul><li>The 2 extra phosphates are lost and this provides the energy to bond one nucleotide to another </li></ul></ul>
  17. 17. histone protein DNA strand DNA wrapped around histones DNA-histone complex folded folding again folding yet again chromosome : very densely packed DNA and proteins structure of chromosome DNA + proteins
  18. 18. DNA gene = a discrete unit of hereditary information (DNA) locus = location of a gene on a chromosome
  19. 19.
  20. 20. <ul><li>At the end of interphase when DNA replication has been completed, the cell begins mitosis </li></ul><ul><li>In mitosis the nucleus divides to form two genetically identical nuclei </li></ul><ul><li>Towards the end of mitosis, cytoplasm of the cell starts to divide, eventually two cells are formed, each containing one nucleus </li></ul><ul><li>The process of dividing the cytoplasm to form two cells is cytokinesis </li></ul><ul><li>The two cells begin interphase when mitosis & cytokinesis have been completed </li></ul>DNA replication chromosomes condense cell grows and develops