Figure 13 3 Experiment Living S cells Living

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Figure 13. 3 Experiment Living S cells Living R cells (control) Heat-killed S cells

Figure 13. 3 Experiment Living S cells Living R cells (control) Heat-killed S cells Mixture of heat(control) killed S cells and living R cells Results Mouse dies Mouse healthy Mouse dies Living S cells © 2016 Pearson Education, Inc.

Figure 13. 4 Phage head DNA Tail fiber Genetic material Bacterial cell © 2016

Figure 13. 4 Phage head DNA Tail fiber Genetic material Bacterial cell © 2016 Pearson Education, Inc. 100 nm Tail sheath

Experiment Batch 1: Radioactive sulfur (35 S) in phage protein Labeled phages infect cells.

Experiment Batch 1: Radioactive sulfur (35 S) in phage protein Labeled phages infect cells. Agitation frees outside phage parts from cells. Centrifuged cells form a pellet. Free phages and phage parts remain in liquid. Radioactivity (phage protein) found in liquid Radioactive protein DNA Centrifuge Pellet © 2016 Pearson Education, Inc.

Experiment Batch 2: Radioactive phosphorus (32 P) in phage DNA Labeled phages infect cells.

Experiment Batch 2: Radioactive phosphorus (32 P) in phage DNA Labeled phages infect cells. Agitation frees outside phage parts from cells. Centrifuged cells form a pellet. Free phages and phage parts remain in liquid. Radioactive DNA Centrifuge Pellet © 2016 Pearson Education, Inc. Radioactivity (phage DNA) found in pellet

"It has not escaped our notice that the specific pairing we have postulated immediately

"It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material. "

Figure 13. 7 (a) Rosalind Franklin © 2016 Pearson Education, Inc. (b) Franklin’s X-ray

Figure 13. 7 (a) Rosalind Franklin © 2016 Pearson Education, Inc. (b) Franklin’s X-ray diffraction photograph of DNA

© 2016 Pearson Education, Inc.

© 2016 Pearson Education, Inc.

Which are purines? ? ? Which are pyrimidines?

Which are purines? ? ? Which are pyrimidines?

Shows why Chargaff’s rules apply Hydrogen bonds 2 between A and T 3 between

Shows why Chargaff’s rules apply Hydrogen bonds 2 between A and T 3 between G and C

5¢ 3¢ 3¢ A T C G T A A T G C 5¢

5¢ 3¢ 3¢ A T C G T A A T G C 5¢ (a) Parental molecule © 2016 Pearson Education, Inc.

5¢ 3¢ 3¢ 5¢ 3¢ A T C G T A A T G

5¢ 3¢ 3¢ 5¢ 3¢ A T C G T A A T G C 5¢ (a) Parental molecule 3¢ 5¢ (b) Separation of parental strands into templates © 2016 Pearson Education, Inc.

5¢ 3¢ 3¢ 5¢ 3¢ A T A T C G C G T

5¢ 3¢ 3¢ 5¢ 3¢ A T A T C G C G T A T A T G C G C 5¢ (a) Parental molecule 3¢ 5¢ (b) Separation of parental strands into templates © 2016 Pearson Education, Inc. 3¢ 5¢ (c) Formation of new strands complementary to template strands

Parent cell First Second replication (a) Conservative model (b) Semiconservative model (c) Dispersive model

Parent cell First Second replication (a) Conservative model (b) Semiconservative model (c) Dispersive model © 2016 Pearson Education, Inc.

Experiment Bacteria cultured in medium with 15 N (heavy isotope) Results Bacteria transferred to

Experiment Bacteria cultured in medium with 15 N (heavy isotope) Results Bacteria transferred to medium with 14 N (lighter isotope) DNA sample centrifuged after first replication © 2016 Pearson Education, Inc. DNA sample centrifuged after second replication Less dense More dense

Conclusion Predictions: Conservative model Semiconservative model Dispersive model © 2016 Pearson Education, Inc. First

Conclusion Predictions: Conservative model Semiconservative model Dispersive model © 2016 Pearson Education, Inc. First replication Second replication

Animation: DNA Replication Overview © 2016 Pearson Education, Inc.

Animation: DNA Replication Overview © 2016 Pearson Education, Inc.

(a) Origin of replication in an E. coli cell Origin of replication Doublestranded DNA

(a) Origin of replication in an E. coli cell Origin of replication Doublestranded DNA molecule Parental (template) strand Daughter (new) strand Replication fork Replication bubble 0. 5 mm Two daughter DNA molecules © 2016 Pearson Education, Inc.

(b) Origins of replication in a eukaryotic cell Origin of replication Parental (template) strand

(b) Origins of replication in a eukaryotic cell Origin of replication Parental (template) strand Bubble Double-stranded DNA molecule Daughter (new) strand Replication fork 0. 25 mm Two daughter DNA molecules © 2016 Pearson Education, Inc.

Primase Topoisomerase 3¢ 5¢ 5¢ 3¢ RNA primer Replication fork 3¢ 5¢ Helicase Single-strand

Primase Topoisomerase 3¢ 5¢ 5¢ 3¢ RNA primer Replication fork 3¢ 5¢ Helicase Single-strand binding proteins © 2016 Pearson Education, Inc.

DNA Polymerase • Enzyme that adds DNA nucleotides for replication • Has some “quirks”

DNA Polymerase • Enzyme that adds DNA nucleotides for replication • Has some “quirks” – Can only add to a pre-existing chain – Can only add to the 3’ end of a chain How are these problems overcome? -Use an RNA primer as the first segment of the new chain (later replaced by DNA) - PRIMASE is the enzyme that does this

Animation: Leading Strand © 2016 Pearson Education, Inc.

Animation: Leading Strand © 2016 Pearson Education, Inc.

Overview Origin of replication Leading strand Lagging strand Primer Lagging strand Overall directions of

Overview Origin of replication Leading strand Lagging strand Primer Lagging strand Overall directions of replication Leading strand Origin of replication 3¢ 5¢ 5¢ 3¢ RNA primer 3¢ 5¢ Parental DNA pol III 3¢ 5¢ 5¢ 3¢ © 2016 Pearson Education, Inc. Continuous elongation in the 5¢ to 3¢ direction 3¢ 5¢

What about that second problem? Not a problem for one The other strand has

What about that second problem? Not a problem for one The other strand has of the templates to be synthesized (original DNA chain) backwards

Animation: Lagging Strand © 2016 Pearson Education, Inc.

Animation: Lagging Strand © 2016 Pearson Education, Inc.

Animation: DNA Replication Review © 2016 Pearson Education, Inc.

Animation: DNA Replication Review © 2016 Pearson Education, Inc.

Leading strand template DNA pol III Parental DNA 3¢ 5¢ 5¢ 3¢ 3¢ 5¢

Leading strand template DNA pol III Parental DNA 3¢ 5¢ 5¢ 3¢ 3¢ 5¢ 5¢ Connecting protein 3¢ Helicase DNA pol III Lagging strand template Leading strand 3¢ 5¢ Lagging strand Overall direction of replication © 2016 Pearson Education, Inc.

Animation: DNA Replication © 2016 Pearson Education, Inc.

Animation: DNA Replication © 2016 Pearson Education, Inc.