Weekly notes BSC 2010
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This 8 page Class Notes was uploaded by Meghan Cooper Mendes de Oliveira on Sunday October 25, 2015. The Class Notes belongs to BSC 2010 at Florida State University taught by Dr. Steven Marks in Fall 2015. Since its upload, it has received 13 views. For similar materials see Biological Science in Biological Sciences at Florida State University.
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Date Created: 10/25/15
Exam 3 Notes Thursday September 17 2015 BSC 2010 0001 Chapter 16 Molecular Basis of lnhcritancc DNA Replication Background Importance Control Mechanism Initiation Elongation Termination Other Considerations Different types of genomes Replication errors Why does a cell make copies of its DNA DNA contains more information that RNA or Protein Exam 3 Notes Thursday September 17 2015 It is the only biological molecule that can copy itself SemiConservative Replication 5 3 iii9iii iii9iii9 yTAACCTGTACATGGCATTGC 5 5 3 hydrogen ATTGGACATGTACCGTAACIJCIB bonds I I I I I I I I I I I I I I I I I I TAACCTGTACATGG CATTG C 3 5 5 3 T GGACATGTACCGTAACG I I I I I I I I I I I I I I I I I I A 1 Parent First Second 3 cell replication replication a Sggiervative lt m W m m mltm b S 39 t39 meDrg clonservaive lt gt gt c Dispersive model Conservative model the original DNA is completely conserved Semiconservative model Exam 3 Notes Thursday September 17 2015 DNA split in half Dispersive model Original DNA is not preserved in anyway Matthew Meselson and Franklin Stahl performed experiments at Cal Tech supported the SemiConservative model labeled nucleotides of the old strands with Nitrogen 15 new nucleotides labeled with Nitrogen 14 Control of DNA Replication Speci c amount of DNA in each cell Diploid cells 2 copies of each chromosome More or less than the original DNA is not tolerated by the cell Cell division is the only time cells replicated DNA Replication DNA sequences recruit proteins needed for replication Proteins create a starting point for replication Proteins recruited Helicase Unwinds DNA Exam 3 Notes Thursday September 17 2015 Single Strand Binding Protein Stabilizes Single Strand DNA Primase Adds an RNA primer Topoisomerase induces supercoils in DNA to counteract supercoils created by unwinding Polymerase catalyze elongation of new DNA Ligase New DNA Strand synthesis DNA Polymerase an enzyme catalyzes the elongation of new DNA DNA polymerase requires a primer and a DNA template add nucleotides only to free 3 end of a growing strand new DNA can only be elongated only in the 5 to 3 direction Leading Strand Synthesis Leading strand synthesis is continuous in the 5 to 3 direction lagging strands strand copied in the opposite direction DNA polymerase works away from the replication fork to elongate the other new strand Exam 3 Notes Thursday September 17 2015 Primase assembles new primers Synthesized by DNA polymerase III as series of segments or Okazaki Fragments Resolution of DNA RNA Hybrid RNA primers have to be replaced by DNA To Remove RNA nucleotides DNA Polymerase removes RNA and fills the gap with DNA nucleotides DNA Ligase joins the 5 end of one DNA molecule to the 3 end of another Termination of Replication Only Prokaryotes have termination sequences Ter sites 23bp sequences cause termination in Vitro Protein bound to the ter site stops the replication fork from proceeding Different Genomes Different Replication Bacteria prokaryotic circular genome single DNA molecule 1 origin of replication Humans eukaryotic linear genome Multiple linear chromosomes Exam 3 Notes Thursday September 17 2015 Multiple origins of replication on each chromosome How do Eukaryotes Protect Chromosome Ends Eukaryotic Chromosomal DNA molecules have noncoding nucleotide sequences at their ends called telomeres Telomeres do not prevent shortening of the DNA molecules they stop the erosion of genes at the end of DNA molecules Telomere Shortening and Aging Telomeres are generally shorter in older individuals in somatic cells somatic cell telomeres gene turned off In germ cells telomeric shortening cannot be tolerated Telomerase in germ cells maintain telomeres at their original length protective against cancer by limiting cell division telomerase activity within tumor cells may be oncogenic Proofreading replication errors once every 100000 nucleotides DNA polymerase will add the wrong nucleotide DNA Pol l and DNA Pol 111 have 3 and 5 exonuclease activity allows them to remove mistaken nucleotide when it s added Extraordinary fidelity considering rate of nucleotide incorporation 50 nucleotides sec Human polymerase 500 nucleotides sec Bacterial polymerase Exam 3 Notes Thursday September 17 2015 Important Replication Proteins Helicase Unwinds DNA to create two single strands Single Strand Binding Protein SSB Binds to and stabilizes the single stranded DNA Primase Provides an RNA primer to start new DNA strand synthesis Topoisomerase Travels ahead of helicase nicking and swiveling the DNA to relieve torsional strain on the molecule Polymerase Ill Assembles new DNA strand in the 5 3 direction Polymerasel Can remove RNA nucleotides as it adds new DNA in a 5 3 direction Ligase Joins two DNA strands together at their ends Telomerase Maintains telomere length in germline cells to protect the health of gametes Chromosomes have a DNA molecule packed with Proteins Bacteria chromosomes are doublestranded circular DNA molecules small amount of protein Eukaryotic chromosomes have linear DNA large amount of histone proteins In bacterium DNA is supercoiled found in the part of the cell call the nucleoid Chromatin DNA and protein complex found in eukaryotic nucleus undergoes changes in packing during cell cycle Exam 3 Notes Thursday September 17 2015 organized into 10nm ber compacted into 30 nm ber by folding and looping must be pack more tightly into pairs of chromatids in preparation of cell division loosely packed during interphase and condenses in mitosis loosely packed chromatin called euchromatin during interphase few regions are highly condensed into heterochromatin dense backing makes it difficult for the cell to express genetic information in these regions
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