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DNA Replication

DNA Replication. Structure of DNA. 1953 | 1962. Watson & Crick developed double helix model of DNA other leading scientists working on question: Rosalind Franklin Maurice Wilkins Linus Pauling. Wilkins. Pauling. Franklin. 1953 article in Nature. Watson and Crick. Watson. Crick.

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DNA Replication

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  1. DNA Replication

  2. Structure of DNA 1953 | 1962 • Watson & Crick • developed double helix model of DNA • other leading scientists working on question: • Rosalind Franklin • Maurice Wilkins • Linus Pauling Wilkins Pauling Franklin

  3. 1953 article in Nature Watson and Crick Watson Crick

  4. Rosalind Franklin (1920-1958)

  5. Double helix structure of DNA “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Watson & Crick

  6. Semiconservative DNA Replication

  7. Base pairing in DNA • Purines • adenine (A) • guanine (G) • Pyrimidines • thymine (T) • cytosine (C) • Pairing • A : T • 2 bonds • C : G • 3 bonds

  8. Copying DNA • Replication of DNA • base pairing allows each strand to serve as a template for a new strand • new strand is 1/2 parent template & 1/2 new DNA • semi-conservativecopy process

  9. Replication: 1st step • Unwind DNA • helicase enzyme unwinds part of DNA helix replication fork

  10. Replication: 2nd step • Build daughter DNA strand • add new complementary bases • Wih the help of DNA polymerase III DNA Polymerase III

  11. Fast & accurate! • It takes E. coli <1 hour to copy 5 million base pairs in its single chromosome • divide to form 2 identical daughter cells • Human cell copies its 6 billion bases & divide into daughter cells in only few hours • remarkably accurate • only ~1 error per 100 million bases • ~30 errors per cell cycle

  12. 1 2 3 4 What does it really look like?

  13. Transcription fromDNA nucleic acid languagetoRNA nucleic acid language

  14. How Are Different Types of Cells Created and Maintained? By differential gene expression. The same genetic information is in all 100 trillion cells of any one person. Different cells use the same blueprint in different ways. How? by regulating the flow of information from DNA to protein.

  15. RNA • ribose sugar • N-bases • uracil instead of thymine • U : A • C : G • single stranded transcription DNA RNA

  16. RNA RNA is a nucleic acid that uses a different sugar than DNA and the base uracil (U) in place of thymine (T).

  17. RNA Is Single-Stranded which allows it to travel in and out of the nucleus

  18. There are Different RNAs with Distinct Functions

  19. Matching bases of DNA & RNA Match RNA bases to DNA bases on one of the DNA strands RNA polymerase A C U G A G G U C U U G C A C A U A G A C U A 5' 3' G C C A T G G T A C A G C T A G T C A T C G T A C C G T

  20. Transcription RNA polymerase acts here RNA polymerase The enzyme RNA polymerase opens the DNA strands and synthesizes an RNA complementary to only one of the DNA strands.

  21. Transcription A gene The decision to transcribe a gene is the most important step in the control of gene expression. Transcription starts and stops at distinct sites at the ends of a gene.

  22. The “Central Dogma” translation transcription RNA DNA protein trait DNA gets all the glory, but proteins do all the work! replication • Flow of genetic information in a cell • How do we move information from DNA to proteins?

  23. From gene to protein aa aa aa aa aa ribosome aa aa aa aa aa aa cytoplasm nucleus transcription translation DNA mRNA protein trait

  24. Any Questions??

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