Molecular Genetics DNA The Genetic Material. Outline: Molecular Genetics

Transcription

1 Molecular Genetics DA The Genetic Material utline: Molecular Genetics istorical Experiments hemical ature of ucleic Acids Replication of DA RA synthesis rotein Synthesis Gene Technology Mutation & ancer Studies Leading to Discovery of DA as Genetic Material bservations of Meiosis hromosomal Theory of Inheritance bservations of totipotency Vegetative growth rchid callus opyright The McGraw-ill ompanies, Inc. ermission required for reproduction or display. Griffith s Experiments & Bacterial Transformation Infect bacteria with Streptococcus pneumoniae Live virulent strain Live nonvirulent strain eat-killed virulent strain Mixture of heat-killed virulent and live nonvirulent strains + olysaccharide coat bservations of uclei Acetabularia Acetabularia Bacterium reproduction Virulence in Streptococcus Virus Reproduction ershey-hase Experiment (1) (2) (3) (4) Mice die Mice live Mice live Mice die & lungs contained live virulent strain 1

2 Avery MacLeod & Mcarty (1944) Extend Griffith s work Bacteriophage Structure urified Extracts of Virulent Bacteria Digestive enzymes use to Remove lipid Remove protein Remove RA Remove DA Virulence remained Transforming ability destroyed rotein ead Tail Tail fiber DA 300,000 opyright 2005 earson Education, Inc. ublishing as Benjamin ummings ershey & hase: Bacteriophage Replication ershey & hase: Bacteriophage Replication 2

3 ucleotide Structure itrogenous bases of DA 4 hosphate Thymine (T) ytosine () Adenine (A) Guanine (G) 2 Base 3 4 Deoxyribose 1 yrimidines urines 2 opyright 2005 earson Education, Inc. ublishing as Benjamin ummings Sugar-hosphate Linkage Between ucleotides Start Monday 11/3/08 3

4 hargaff s Rule X-Ray rystallography Ratio A:T Ratio G: 1. Rosalind Franklin Maurice Wilkins DA was helical DA had repetitive elements 0.34 nm, 3.4 nm, 2.0nm opyright The McGraw-ill ompanies, Inc. ermission required for reproduction or display. James Watson & Francis rick ropose a Double elix hargaff s Rule made sense! ydrogen bonds between nitrogenous bases hosphodiester bond G A G T A end end Sugar-phosphate "backbone" T Double elix Structure of DA rystallography data made sense! Major groove 3.4 nm Distance between base pairs 0.34 nm Minor groove Diameter of DA 2.0 nm 4

5 Summary DA Structure DA Replication is Semi-onservative 1. Two nucleotide chains sugar-phosphate backbone 2. Bases complementary A-T and G- 3. Double elix 4. Antiparallel ends opposite DA Synthesis: Addition of ucleotides Template ew Template G ew G T A T A ydrogen bonds DA stabilize bases Free ucleotide A T olymerase A T pairs with III complementary base G G A A T T A A DA olymerase forms hosphodiester bond Fig (TE Art) Leading Strand ontinuous Synthesis opyright The McGraw-ill ompanies, Inc. ermission required for reproduction or display. kazaki fragment DA Replication DA polymerase III Lagging Discontinuous Synthesis 5

6 Fig (TE Art) Leading opyright The McGraw-ill ompanies, Inc. ermission required for reproduction or display. Enzymes in DA Replication 4. DA polymerase III 2. Single- Adds ucleotides to binding proteins Leading Strand Stabilize DA Single DA Synthesis 8. DA ligase Joins kazaki Fragments Lagging kazaki fragments 7. DA olymerase I Removes RA rimer & fills gap 6. DA olymerase III Adds ucleotides To End arental DA helix 1. elicase Unwinds DA 3. Gyrase Relieves Torque 5. rimase adds RA primer Replisome All enzymes for DA replication Speed of DA Synthesis - rokaryotes rokaryotes E. coli genome contains 4.7 x 10 6 nucleotide pairs Speed = 1000 nucleotides per second DA replication is bidirectional Total time 40 minutes start to finish. Speed of DA Synthesis - Eukaryotes opyright The McGraw-ill ompanies, Inc. ermission required for reproduction or display. Eukaryotic DA Replication Many Replication Forks Eukaryotes Each human chromosome 150 x 10 6 nucleotide pairs 50 nucleotide pairs per second arent oint of separation Daughter Total time one month? umerous replication forks per chromosome one hour start to finish. 6

7 ompletion of DA Synthesis on Lagging Strand Telomerase Adds Telomeric DA to hromosomes Stained Telomeric DA (TTAGGG) n thousand base pairs ED DA istory & DA Synthesis 7