ch. 12 Flashcards
1 error/million bp leads to ___ mistakes. Thus replication is accurate and____.
6,400
Fast (E coil is 1000 nucleotides/second)
DNA replication is
A. semiconservative
B. Dispersive
C. Conservative
Semiconservative
Who discover Semiconservative?
Meselson and Stahl: 2 types of nitrogen. (Try and understand this)
Replication Model: Theta
Circular, bi or unidirectional, No strand breakage, 1 replicon, makes 2 circular molecules
Replication Model: Rolling Circle
Circular, unidirection, 1 replicon, nucleotide strand breakage, 1 circular + 1 linear
Replication Model: Linear
Linear, No breakage, bidirectional, many replicons, 2 linear
Nucleotides only added to
3’ end, 5’ –> 3’ direction
Initiator protein
bind to oriC in in bacterial and cause short section of DNA to unwind.
DNA helicase
Breaks the hydrogen bonds that exist between the bases of the two nucleotide strands of a DNA molecule
SSBs
Protect single strand, prevent 2ndary structures
DNA gyrase/Topoimerase
Supercoiling, type 2, double stranding
Reduces torque, removes supercoiling through strand breaks. If not, DNA is highly twisted.
Primase
Synthesizes short stretches of RNA nucleotides or primers which provide a 3’-OH group to which DNA polymerases can attach DNA nucleotides.
Where do primers go?
Leading strand 5’ end. Beginning of each okazaki fragment
DNA polymerase 3
Elongates DNA from 3’-OH strand provided by primer.
5–>3 polymerase: fill in gaps caused by RNA primers
3–>5 exonuclease: correct errors, increase polymerase fidelity
D
DNA polymerase 1
Remove RNA primers and replace them with DNA
5-3 polymerse: fill gaps by RNA primers
3-5 Exo: correct errors
5-3 Exo: RNA primer removal
