Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Fig. 7-1Chapter 7: DNA structure and replicationFROM GENE TO PROTEINReplication: DNA-dependent DNA synthesis; DNA polymerase and associated proteins; DNA template, dNTPsTranscription: DNA-dependent RNA synthesis; RNA polymerase and associated proteins; DNA template, NTPsTranslation: RNA-dependent polypeptide synthesis; ribosome and associated molecules; mRNA, ribosomes,aminoacyl-tRNAFig. 7-2Griffith (1928): Streptococcal transformationFig. 7-3Avery, MacLeod & McCarty (1944): Griffith’s “transforming principle” is DNAFig. 7-5Background information available to Watson & Crick in construction of their double-helical DNA model1. E. Chargaff’s “rule” (A=T, G=C)Background information available to Watson & Crick in construction of their double-helical DNA model1. E. Chargaff’s “rule” (A=T, G=C)2. Wilkins & Franklin’s x-ray diffraction data (suggested strongly helical, probably double-helical structure)Fig. 7-8Major grooveMinor grooveFig. 7-8DNA double helix is stabilized by:1. Hydrophobic interactions among bases2. Hydrophilic interactions of PO4 with aqueous environment3. Hydrogen bonds between complementary bases (A-T pair, two H bonds; G-C pair, three H bonds)Fig. 7-12Potential modes of DNA replicationFig. 7-13Fig. 7-155’-3’ synthesis of DNA proceeds by 3’ extension and complementary base pairingFig. 7-16Replication fork dynamics creates polarity problems in lagging strand synthesisFig. 7-17Fig. 7-18Replication fork dynamics depends upon cooperative activities of a variety of proteinsFig. 7-22Chromosome replication is carried out by expansion of “bubbles”Fig. 7-24DNA synthesis creates problems at chromosome endsEver-shortening 5’ endsFig. 7-25Telomerase is special DNA polymerase that maintains chromosome endsTelomeres consist of high-copy number, simple sequence repeatsFig. 7-Human haploid genome  1 m of DNA (about 2 m DNA per somatic cell*) (about 4.3 cm DNA per chromosome)* ~1013 somatic cells per average human ~ 2 x 1013 m of DNA per average human (nearly 100 round trips to the sun!!)Human haploid genome  1 m of DNA (about 2 m DNA per somatic cell*) (about 4.3 cm DNA per chromosome)* ~1013 somatic cells per average human ~ 2 x 1013 m of DNA per average human (nearly 100 round trips to the sun!!)Average human nucleus ~ 6 μm diameter Eukaryotic DNA is densely