* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download TElomere Reverse Transcriptase
Survey
Document related concepts
Zinc finger nuclease wikipedia , lookup
DNA repair protein XRCC4 wikipedia , lookup
DNA sequencing wikipedia , lookup
Homologous recombination wikipedia , lookup
Eukaryotic DNA replication wikipedia , lookup
DNA profiling wikipedia , lookup
DNA nanotechnology wikipedia , lookup
Microsatellite wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
DNA replication wikipedia , lookup
DNA polymerase wikipedia , lookup
Transcript
REPLICATION OF DNA 1. Origins of replication-specific nucleotide sequences along the DNA molecules to which certain proteins (DNA B) can attach and begin replication; hundreds per eukaryotic chromosome. 2. Replication forks- the Y-shaped places where DNA is being unzipped by helicases; replication is bidirectional; two replication forks form at each origin and move in both directions. 3. Helicases-enzymes that break the H bonds linking the complementary bases and unzip the two sides of the helix. 4. Topoisomerases (swivelases) breaks one side of the helix ahead of where helicase is unzipping it and allows it to swivel and untwist to relieve the strain. 5. Single strand binding proteins (SSB)-attach to the backside of each of the unzipped strands and hold them apart and keep them from kinking. REPLICATION OF DNA 6. RNA primase-enzyme which lays down a short piece of RNA primer to provide a 3’ end for DNA polymerase III to start from. Neither of the DNA polymerases can start from “scratch” they can only add nucleotides to an existing 3’ end. 7. DNA polymerase III-actually a complex of several enzymes; it is fast but can only attach new nucleotides to the 3’ end of an existing strand; also can not fill in the last 3-5 nucleotides in a gap 8. DNA polymerase I-much slower removes the RNA primer nucleotides and replaces them with DNA nucleotides attaching them to the 3’ of the last Okazaki fragment, it is also used in repair 9. Leading Strand-side of the new DNA which has a 3’ end to which DNA polymerase III can attach and rapidly add new nucleotides after only one short RNA primer is added REPLICATION OF DNA 10. Lagging Strand-side with a 5’ end, thus new RNA primers must be added every 100-200 nucleotides, so the DNA pIII can attach DNA nucleotides to the 3’ end working back toward the origin of replication 11. Okazaki fragments-sections of DNA 100-200 nucleotides long which are formed on the lagging strand between primers, after DNA pIII runs into the next primer it pulls out and DNA pI comes in, removes the RNA primer and replaces it with DNA but it cannot make the last bond between the sugar and phosphate 12. DNA Ligase-enzyme that connects the new DNA segment to the growing DNA strand, by joining the last sugar and phosphate together http://www.dnaftb.org/dnaftb/ P.A. Levene-a prominent molecular biologist in the 40’s. He determined the structure of a nucleotide but then proposed that it was a tetranucleotide(wrong) which each contained one of each nitrogen base. Many biologists believed his theory. Chargaff- % of adenine = % of thymine % of guanine = % of cytosine implied that A was always found with T and C was found with G Linus Pauling-determined the alpha helix of proteins but was trying to make a triple helix which obviously did not work Rosalind Franklin was a graduate student working for Maurice Wilkins. She did the best X-ray diffraction studies but never got the credit. 5’end 3’ end 3’ end 5’ end strands are antiparallel Crick 5’ phosphodiester bond 3’ F1 All 14N DNA All 15N DNA From bacteria grown on 14N for generations Mixture 15N From bacteria and 14N grown on 15N for generations DNA basic controls F2 All DNA ½ 15N ½ 14N ½ DNA(½ 15N ½ 14N) ½ 14N DNA bacteria with bacteria with all all 15N DNA grown on light for one 15N generation DNA grown on 14N for 2 generations http://science.nhmccd.edu/biol/ap1int.htm origin of replication topoisomerase origin of replication helicase topoisomerase RNA primers RNA DNA ligase Telomerase is an enzyme that adds telomere repeat sequences to the 3' end of DNA strands. By lengthening this strand DNA polymerase is able to complete the synthesis of the "incomplete ends" of the opposite strand. Telomerase: is a ribonucleoprotein. Its single snoRNA molecule — called TERC ("TElomere RNA Component") — provides an AAUCCC (in mammals) template to guide the insertion of TTAGGG. Its protein component — called TERT ("TElomere Reverse Transcriptase") — provides the catalytic action. Thus telomerase is a reverse transcriptase; synthesizing DNA from an RNA template. Telomerase is generally found only in the cells of the germline, including embryonic stem (ES) cells; unicellular eukaryotes like Tetrahymena thermophila; some — perhaps all — "adult" stem cells and "progenitor" cells enabling them to proliferate; cancer cells. Telomeres