Lecture #11- DNA Chemistry and Replication

Question 1

properties of genetic material and why wasn’t DNA thought to be the universal hereditary material

Answer 1

1. carry info
2. replicated faithfully and transmit info
3. have variation

• proteins with 20 possible monomers seems more likely because of the variation

Question 2

explain the Griffiths Transformation Experiment

Answer 2

• 1928
• showed that non-living component of cells was able to transform other cells
• “is there a transforming principle?”
• Experiment: took 2 strains of bacteria (same species with different properties)
  1. Rough (R) strain -> non- virulent (non-disease causing)
  2. S (smooth) strain -virulent (disease causing)
• conclusion: there is an abiotic transforming principle

Question 3

explain the Avery, MacLeod and McCarty experiment

Answer 3

• “what is the transforming principle?”
• use different enzymes to specifically degrade cellular components
• Pipases or sucrases, RNase, Protase, DNase
• conclusion: DNA is the transforming principle

Question 4

Explain Hershey and Chase (Phage-in-a-blender)

Answer 4

• uses a phage (virus that infect bacteria)
• use radioactivity as a was to trace DNA and protein
• P32 tracks DNA, S35 tracks protein
• P32, there was radioactivity the pelle, DNA entered the bacteria to transform it
• conclusion: DNA is the universal transforming principle

Question 5

Explain Meselson- Stahl experiment and draw it out

Answer 5

• attempted to determine which hypothetical process of DNA replication was correct - semi-conservative, conservative or dispersive
• used radioactive to change the molecular mass of - compared the expected to the observed
• conclusion: DNA replicates semi-conservatively

Question 6

3 rules to understand DNA replication

Answer 6

1. DNA is antiparallel 5’ -> 3’ and 3’ -> 5’
2. DNA polymerase only extends 5’ -> 3’
3. DNA poly requires an existing 3’ OH
   - DNA poly catalyze phosphodiester bond formation

Question 7

Draw and label, replication bubble, direction of the fork opening, leading strand, Okazaki fragments, lagging strand

Answer 7

pg 10

Question 8

Draw DNA Replication in detail, include helicase, SSB’s, primase, DNA polymerase III, DNA poly I, ligase