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Flashcards in DNA Chemistry and Replication Deck (22)
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What was the question asked in Griffiths Transformation Experiment?

Is there a transforming principle?


Explain briefly how Griffiths underwent his experiment

Took rough and smooth strains, S was virulent and R was not. He injected them both into mice, the S strain killed the mouse. A heat killed S strain did not kill the mouse, but when mixed with R strain it did. This is because the R strain picked up the ability to cause disease from the environment (it transformed).


What was Avery, MacLeod and McCarty's experimental question?

What is the transforming principle?


Explain Briefly how A, M, M underwent their experiment

Used different enzymes for degradation of cellular components (protease, Dnase, Rnase) Injected mice with heat killed S strain and R strain, the one with Dnase lived. Therefore DNA is the transforming principle, not proteins.


What was Hershey and Chases question

Is DNA the universal transforming principle?


Briefly explain H and C's experiment

Used virus that infects bacteria (phage) to label proteins and DNA (S35 for proteins, P32 for DNA), found that the viral DNA enters the bacterial cell and the viral proteins do not (DNA's pellet was radioactive)


What is Chargaffs rule



What did James Watson and Francis Crick discover

-DNA is a double helix (used work of others: Chargaff and Rosalind Franklin)
-A pairs with T, C pairs with G


What are the three forces that stabilize DNA

1. Phosphodiester bonds
2. H-bonds
3. Hydrophobic base pairing


When does DNA replication occur

S phase


What did Meselson-Stahl attempt to detemine

Is DNA replication conservative, semiconservative or dispersive (can you picture the models in your head?)


Briefly Describe Meselson-Stahl's experiment

Used radioactivity to change molecular mass of N (N15= heavy nitrogen). One round of replication in N14 lead to observed intermediate band, conservative rep was disproved. Second round of replication in N14 led to one N14 band and one N14.5 band. Rules out dispersive cause we would have expected N14.25 band.


What direction is DNA polymerized

5' -> 3' (nucleotides added to 3' end)


What is deoxyribonucleotide?

substrate of replication


What is the enzyme of replication and what does it do

DNA polymerase
catalyzes phosphodiester bond formation


What enzyme unwinds the double helix



What is the role of DNA polymerase III

Adding nucleotides (in the 3' to 5' direction)


What keeps the bubble unwound?

Single stranded binding proteins


The ______ strand is synthesized discontinuously in small fragments called _______ __________.

1. lagging strand
2. okazaki fragments


What connects the okazaki fragments?

DNA ligase


What is the role of primase in replication

Synthesizes an RNA primer at 5' end of lead strand and each okazaki fragment.


What is the role of polymerase I?

Remove RNA nucleotides that primase put at the 5' end and replaces them with DNA nucleotides