1 / 9

16B

16B. DNA Replication and Repair. Semiconservative Model. Separate DNA Strands, each side serves as a template for a new strand New nucleotides join according to _____ and ______. Nucleotides are connected-new DNA formed (one old strand and one new strand). Meselson Stahl Test.

kay
Download Presentation

16B

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 16B DNA Replication and Repair

  2. Semiconservative Model • Separate DNA Strands, each side serves as a template for a new strand • New nucleotides join according to _____ and ______. • Nucleotides are connected-new DNA formed (one old strand and one new strand)

  3. Meselson Stahl Test • If conservative: parent in tact • If dispersive: all 4 strands should have old and new • If semiconservative, half old strand and new strand and half new strand • Semiconservative proved true • Funny story • http://www.youtube.com/watch?v=MX5FrexyQyo

  4. Origins of replication • 1 in prokaryotes, many in eukaryotes, form bubbles • _____________: enzyme that opens DNA strand • _____________: point of replication “unzipping”

  5. DNA Polymerase Adds New Nucleotides • Nucleotides start as nucleoside ____________________ (like ______) • Lose two phosphate groups, energy drives nucleotide joining • The two DNA strands are _________________: sugar and phosphate sides run in opposite directions. One side has 5prime on top and 3 prime on bottom, other has 3prime on top and 5prime on bottom.

  6. Elongation • DNA polymerase adds nucleotides ONLY to the ________ end of a growing DNA strand. New DNA always elongates in the ____ to ____ direction. • Leading strand: DNA polymerase adds in the _____ to ____ direction, goes with the fork. • Lagging strand: DNA polymerase makes short segments in the ____ to ____ direction called ____________ fragments (100-200 bases long); fragments are joined by __________________. • http://www.youtube.com/watch?v=teV62zrm2P0

  7. Priming DNA synthesis • DNA polymerases can only add to existing polynucleotides, can’t start one. • ___________: about 10 nucleotides of RNA that are joined by the enzyme ___________; are eventually replaced by DNA. • _____ primer for the leading strand; one primer for EACH Okazaki fragment in the ________________________.

  8. DNA Repair • Mismatch: DNA polymerase proofreads, other proteins proofread as well. • Repair of existing DNA is called excision repair: _______________(DNA cutting enzyme) cuts out the damaged section, DNA polymerase and ligase add new nucleotides to refill area. Ex. Thymine dimers caused by UV radiation.

  9. Ending Replication • DNA polymerases can’t complete 5 prime ends; DNA strands would shorten over time. • Eukaryotes: ___________ at ends. Multiple repetitions of sequence, usually TTAGGG (no genes) • _________________: enzyme that lengthens telomeres; has RNA along with its proteins • Telomerase may be in cancer cells, giving them immortality.

More Related