1. Molecular Biology of the Gene Chapter 10

2. Viruses are biological saboteurs Hijacking the genetic material of host cells in order to reproduce themselves Viruses provided some of the earliest evidence That genes are made of DNA

3. Griffith Discovers Transformation 1928 Attempting to develop a vaccine he isolated two strains of pneumonia Rough strain was harmless Smooth strain was pathogenic

4. Griffith Discovers Transformation

5. Transformation The harmless R cells had been transformed by material from the dead S cells Descendents of the transformed cells were also pathogenic

6. 10.1 Experiments showed that DNA is the genetic material The Hershey-Chase experiment showed that certain viruses reprogram host cells To produce more viruses by injecting their DNA Head Tail Tail fiber DNA 300,000 

7. Bacteriophages Viruses that infect bacteria Consist of protein and DNA Inject their hereditary material into bacteria

8. The Hershey-Chase experiment

9. 10.2 DNA and RNA are polymers of nucleotides DNA is a nucleic acid Made of long chains of nucleotide monomers DNA polynucleotide A C T G T Sugar-phosphate backbone Phosphate group Nitrogenous base Sugar A C T G T Phosphate group O O–O– O O P CH 2 H3CH3C C C C C N C N H H O O C O O H C H H H C H Nitrogenous base (A, G, C, or T) Thymine (T) Sugar (deoxyribose) DNA nucleotide

10. DNA has four kinds of nitrogenous bases A, T, C, and G C C C C C C O N C H H O N H H3CH3C H H H H N N N H O C HH N H C N N N N C C C C H H N N H C C N C H N C N HC O H H Thymine (T)Cytosine (C) Adenine (A) Guanine (G) Purines Pyrimidines

11. RNA is also a nucleic acid But has a slightly different sugar And has U instead of T Nitrogenous base (A, G, C, or U) Phosphate group O O–O– OOPCH 2 H C C C C N C N H H O O C O O H C H H OH C H Uracil (U) Sugar (ribose) Key Hydrogen atom Carbon atom Nitrogen atom Oxygen atom Phosphorus atom

12. DNA is a double-stranded helix James Watson and Francis Crick Worked out the three-dimensional structure of DNA, based on work by Rosalind

13. GC TA AT G G C C A T GC T A T A AT AT GC A T O O OH –O–O P O O –O–O P O O O P – O O P O O O OH H2CH2C H2CH2C H2CH2C H2CH2C O O O O O O O O P O–O– O–O– O–O– O–O– HO O O O P P P O O O O O O O O T A G C C G AT CH 2 Hydrogen bond Base pair Ribbon model Partial chemical structure Computer model Hydrogen bonds between bases Hold the strands together Each base pairs with a complementary partner A with T, and G with C

14. DNA Replication DNA replication depends on specific base pairing DNA replication Starts with the separation of DNA strands Then enzymes use each strand as a template To assemble new nucleotides into complementary strands A T C G G C A T T A AT C G G C A T T A A T C G G C A T T A A T C G G C A T AT C G A C T A Parental molecule of DNA Both parental strands serve as templates Two identical daughter molecules of DNA

15. DNA Replication DNA replication is a complex process Due in part to the fact that some of the helical DNA molecule must untwist GC A T GC AT C G A G A C G C G C G T A G C T A T A A T T A C G C G C G T A G C T A T A A T T A T C T

16. DNA Replication DNA replication Begins at specific sites on the double helix Origin of replication Two daughter DNA molecules Parental strand Daughter strand Bubble

17. DNA Replication Each strand of the double helix Is oriented in the opposite direction (antiparallel)

18. DNA Replication Using the enzyme DNA polymerase The cell synthesizes one daughter strand as a continuous piece The other strand is synthesized as a series of short pieces Which are then connected by the enzyme DNA ligase

19. DNA Replication