Bio 202 Exam 2 Study Guide
Bio 202 Exam 2 Study Guide 20146
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This 3 page Study Guide was uploaded by email@example.com Notetaker on Friday April 1, 2016. The Study Guide belongs to 20146 at Indiana University of Pennsylvania taught by Robert Major in Spring 2016. Since its upload, it has received 14 views. For similar materials see Principles of Cellular and Molecular Biology in Biology at Indiana University of Pennsylvania.
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Date Created: 04/01/16
Biology 202 Exam 3 Study Guide April 4, 2016 1) What is the DNA Structure? -Double Helix Shape -Two anti-parallel strands -1 strand: alternating sugars and phosphates -4 nitrogenous bases: Adenine (purine), Thymine (pyrimidine), Guanine (purine), and Cytosine (pyrimidine) -Adenine pairs with Thymine by two Hydrogen bonds -Guanine pairs with Cytosine by three hydrogen bonds -Anti-parallel strands: 5 prime to 3 prime 5’3’ 3’5’ 3’: hydroxyl group 5’: phosphate group What would the complementary strand of DNA read if?: (5’) C A A G T C A T T (3’) 2) Important Experiments -Transformation Experiment: Frederick Griffith - Two different bacterial strands were injected into mice S Strain killed the mice R Strain did not kill the mice -Both strains are heated and injected into new mice S Strain did not kill the mice S Strain combined with the R Strain did kill the mice -The results of the heated strains show that DNA is the only transformable molecule Only the DNA extract from the S Strain could transform the R strain -Blender Experiment: Hershey and Chase -Used virsuses to attack bacterial cells -Each virsus’s DNA and proteins were labeled with radioactive phosphorus and sulfur DNA: radioactive 32P Proteins: radioactive 35S -Virsus was “blended” together Only transfer seen was the DNA 3) How are chromosomes structured? -Humans have 23 pairs of chromosomes, one from each parent per pair -Organized like “beads on a string” DNA packaged with proteins to form chromatin -Chromosomes packaged into nucleosomes Pulled together after packaging by histone HI Can either be highly or not highly condensed -euchromatin: not highly condensed -heterochromatin: high condensed 4) What controls chromatin structure? -Histones contain a large amount of positively charged amino acids that interact well with DNA’s negatively charged phosphate Lysine Arginine Histidine -Masking the positive charge on the histone can loosen the DNA/histone interaction -Histones have “tails” that can be covalently modified through: Acetylated Methylated Phosphorylated 5) How is DNA Replicated in Eukaryotic Cells? -Step 1: Where to Start: DNA Helicase unzips the DNA at the replication origin and creates two separate strands -Each of these strands is now a template (1 DNA=2 template strands) -1 strand is 5’-3’ (this will cause problems later) -Other strand is 3’-5’ -The opening that is now created is the replication bubble -Two ends of the replication bubble are the replication forks -Strong concentration of A-T b/c two hydrogen bonds are easier to break than three -Step 2: Fixing problems at the Replication Fork -As the DNA opens up, tension developed downstream of the replication fork, causing the strand to supercoil -Topoisomerase: enzyme that comes and relieves tension built up -Step 3: DNA Synthesis -The bases on the template strand are used to determine the correct number of nucleotides to add (A/U/G/C) -Uracil replaces thymine because the new strand being created is mRNA (messenger RNA and RNA does not have thymine) -This will only form 5’3’ so the new nucleotides will be added to the 3’ end -3’ hydroxyl binds to a 5’ phosphate of a nucleotide tri-phosphate -loses 2 phosphates -Proofreading will also occur to check for mispaired nucleotides -Step 4: (More) Problems at the replication fork: Lagging Strands -Lagging strand: The top template strand is not 5’3’, which causes it to keep starting replication over, rather than continuously replicate -Leading strand: strand that is 5’3’ -To help the Lagging Strand replicate, Okazaki fragments are added to the RNA primer by DNA polymerase -DNA polymerase continues to add nucleotides to the 3’ end of the new RNA primer to start new Okazaki fragments -Okazaki fragments are joined together by ligase -Lagging strand now becomes one continuous strand -Step 5: Almost Done! -Because of the lagging strand having to constantly start over, a gap remains at the end of it -Telomerase synthesizes telomere sequences -Telomere: ends of the lagging strand that fray -1 strand of DNA2 strands of template DNA+mRNA2 new strands of DNA
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