BIO 1201 Exam 3

BIO 1201 Exam 3 - BIO 1201 Exam 3 Material Molecular Basis...

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BIO 1201 Exam 3 Material Molecular Basis of Inheritance A. What is the structure of the genome? i. chromosome and DNA structure B. How is the genome copied? i. DNA replication C. What is the genome used for? i. protein synthesis Eukaryotic Chromosome Structure A. DNA (linear molecule) B. Histone Proteins C. Nucleosomes (beads on a string) D. DNA normally supercoiled into chromosomes, but in replication uncoiled and relaxed DNA Structure and Replication I. Structure of Nucleic Acids (DNA) A. nucleotide structure: four nucleotides B.  nitrogenous bases:  complementary base pairing i.  purines  (a=adenine, g=guanine) (double ring) ii.   pyrimidines  (t=thymine, c=cytosine) (single ring) iii. all species the amount of A=T and G=C, but each species has its own ratio of  AT/GC iv.  hydrogen bonds   C.  Antiparallel double helix E. Mechanism for replication:  semi-conservative II.  PROCESS OF REPLICATION:  (eukaryotes) 1. Replication begins at many replication origins (up to 1,000 per DNA molecule) a. form replication bubbles b. strands must unwind and separate 2.  Topoisomerase b. relieve stress along tightening strands, counteract expanding bubbles caused  by helicase 3.  Helicase  enzymes
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a. unzip and separate DNA, create replication fork 4.  SSB proteins  (single strand binding proteins) a. holds the separated strands apart 5 . Primase  a. now builds a short  RNA primer  (~10 nucleotides) 5' to 3' 6.  DNA polymerase  ( fig. 16.7) a. enzymes now bind to the strand next to the primer and catalyzes the addition  of new nucleotides, one by one b. move only in one direction that is the new strand will always be built from its 5'  to its 3' end. c. leading and lagging strands d. leading strand continuous, lagging strand contains Okazaki fragments e.  DNA Polymerase III:  adds new nucleotides to 3’ end, responsible for actual  synthesis of new strands (both leading and lagging) f.  DNA polymerase I : removes RNA nucleotides of primer from the 5’ end and  replaces them with DNA nucleotides 7.  DNA ligase a. connects Okazaki fragments and any gaps in new strands, fuses different  sections together 8.  Telomerase a. protects ends from shortening and loss of information - during replication III. Three questions of interest concerning this process  1.  What happens if the wrong base is added to the growing strand? - many bases check continuously and early to see if every nucleotide is correct, or later on ( nuclease),  if not then, becomes a mutation 2. Where does the energy for these reactions come from?
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