1. Who are these two famous characters of science?

2. Mendel (1865): Inheritance

3. T.H. Morgan (1910): genes linked on chromosomes Chromosomes are made of DNA and proteins DNA and proteins are the two candidates for the genetic material

4. Griffith(1928): bacterial work- streptococcus pneumoniae Transformation: change in genotype and phenotype due to assimilation of external substance (DNA) by a cell

6. Avery and team(MacLeod and McCarty)(1944): transformation agent was DNA

7. Hershey and Chase(1952): determine that DNA is the hereditary material and not proteins:

8. Chargaff(1950): found “peculiar regularity” in the ratios of nucleotide bases within a single species:  A = 30.3%  T = 30.3%  C= 19.9%  G = 19.5% Chargaff rules: A= T, C= G

9. Watson & Crick(Wilkins, Franklin)(1953): The Double Helix

10. Basic Unit of Nucleic Acids = nucleotide Sugar/ phosphate backbone Nitrogen base

11. 5 carbon sugar = ribose Phosphate group Phosphodiester bond

12. In DNA there are four(make up the interior of the molecule): Adenine Thymine Cytosine Guanine Two groups: Purines: double ringed structures Adenine and Guanine Pyrimidines: single ringed structures Thymine and Cytosine

13. 5’ to 3’ 5’ with the phosphate group 3’ with the –OH group

14. Inward facing nitrogen base will pair with their complementary base A will pair with T (two H- bonds) G will pair with G (three H- bonds) A double ringed structure will always pair with a single ringed structure to maintain width.

16. DNA strands are oriented in the opposite directions

17. Van der Waals attractions play a role in holding the DNA molecule together

19. Proposed the semiconservative model of DNA replication:

20. DNA polymerase Helicase Primase DNA ligase Topoisomerase

21. Sites where DNA replication begins Prokaryotes: one origin Replication proceeds in two directions Humans: hundreds maybe thousands of origins Replication proceeds in two directions

22. Replication bubble: unwinding and separation of the DNA strand Replication fork: Y- shaped region at each end of the bubble

23. 1. 2. 3. 4. ?’?’?’?’ ?’?’?’?’ ?’?’?’?’ ?’?’?’?’ 5.

24. Elongation catalyzed by DNA polymerase E. coli bacteria adds nucleotides at a rate of 500/sec Humans add nucleotides at a rate of 50/sec Nucleoside triphosphate:

25. Antiparallel elonagation: 5’ – 3’ direction Leading strand Lagging strand Okazaki fragments E. coli fragments: 1000- 2000 nucleotides Human fragments: 100 -200

27. Meselson & Stahl replication semiconservative; Expt: varying densities of radioactive nitrogen

28. Briefly describe the role of the following enzymes involved in DNA replication: DNA polymerase I DNA polymerase III Helicase DNA ligase Topoisomerase Primase

29. 1. 2. 3. 4. ?’?’?’?’ ?’?’?’?’ ?’?’?’?’ ?’?’?’?’ 5.

30. How many primers are needed for the leading strand? How many primers are needed for the lagging strand?

31. DNA replication ensures continuity of hereditary information:

32. 1. Enzymes of DNA replication work as part of a large complex: 2. Replication process is probably a stationary process DNA polymerase “reels- in” the parent DNA Lagging strand may may be looped

33. Pairing errors occur at the rate of 1 out of every 100, 000 base pairs DNA polymerase proof reads each nucleotide Incorrectly paired nucleotides are immediately removed and replaced

34. Mismatch pair: Repaired by the action of nuclease(one of many different DNA repair enzymes) Removes nucleotides damaged by chemicals or the environment

35. Telomeres= nucleotide sequences at the ends of the DNA molecule Contain a repeated unit TTAGGG Do not contain genes No nucleotides added Protects the molecule from the replication process Triggers apoptosis May contribute to the aging process

36. Catalyzes the lengthening of the telomeres in eukaryotic germ cells