DNA Replication

Question 1

Central Dogma

Answer 1

DNA–>RNA–>Protein

Question 2

Double helix structure

Answer 2

makes DNA elegantly suited to its function
o Encodes and stores an enormous amount of information in a compact space
o Matching and structure helps to prevent mutation
o Double-stranded nature provides accurate template for reproduction

Question 3

DNA Structure

Answer 3

• DNA can be found in an unwound, condensed form called chromatin
• Chromatin involves a mixture of both DNA and the proteins it winds around
• Some organization to chromatin

Two strands of the DNA molecule are connected by hydrogen bonds between the bases
One nucleotide is joined to the next by a covalent phosphodiester bond between the sugar and phosphate

Question 4

DNA Replication

Answer 4

• DNA is a two stranded molecule
• To replicate, it is unwound and each strand is used as a template for a new strand
• At the end of the process you have 2 new strands: each is half old half new
• Without a template u cannot have replication

Question 5

Steps to replicate DNA

Answer 5

• Unwind DNA (helicase
• Stabilize newly single stranded DNA: single strand binding proteins; makes sure DNA doesn’t refold on itself
• Stabilize the helix ahead of the replication area :topoisomerase
• DNA requires a primer (primase)
o Build a tiny stretch of RNA
o Build DNA sequence from the RNA (DNA replicating enzymes can only add, not initiate) :DNA polymerases add nucleotides
o Later, RNA primase is degraded
o If primase isn’t attached=no DNA replication

Question 6

DNA Polymerase

Answer 6

RNA primer
is very fast
can only go in a 5’–>3’ direction

Question 7

leading strand

Answer 7

one strand (the 3’-5’) strand can proceed continuously, unwinding the helix as replication progresses

Question 8

lagging strand

Answer 8

strands that replicates away from the helicase, so it replicates in fragments

Question 9

okazaki fragments

Answer 9

help with DNA replication

Question 10

different DNA polymerase molecules

Answer 10

o Add nucleotides to the RNA primer or DNA strand
o Replaces the RNA primer with DNA
o Proofreading

Question 11

Proofreading

Answer 11

• As it adds bases, DNA polymerase proofreads and corrects
• Errors that escape proofreading are often caught later
• Adding the wrong base will often cause a size shift in the DNA ladder
• This prevents the addition of a new base until the mistake has been repaired
• DNA POLYMERASE III

Question 12

Mismatch repair

Answer 12

• C could bind with A, w/out a significant shape change

* Second set of proteins (including another DNA polymerase) scans the new molecule for errors