DNA Replication, Repair, and Recombination Flashcards Preview

Med Chem > DNA Replication, Repair, and Recombination > Flashcards

Flashcards in DNA Replication, Repair, and Recombination Deck (22):
1

Semiconservative replication

1 old strand paired with 1 new strand

2

3 steps of DNA replication

1. Initiation (assembly of replication machinery)
2. Elongation (nucleotides are added to growing chains)
3. Termination (replication machinery disassembles; separation of daughter molecules)

3

Longest step in DNA replication

Elongation

4

DNA polymerase I

Repairs DNA and catalyzes the synthesis of the lagging strand

5

DNA polymerase II

Repairs DNA

6

DNA polymerase III

Major DNA replication enzyme

7

Eta subunit of DNA pol III

3' -> 5' exonuclease
Proofreading portion of DNA pol III

8

Beta subunit of DNA pol III

Forms sliding clamp
Portion of DNA pol III that wraps around it

9

How DNA pol III works

Catalyzes formation of a phosphodiester linkage between the dNTP and the growing chain

10

How fast replication takes place

~1000 bp/second

11

Elongation mechanism

Free 3' -OH attacks the alpha-phosphate of the dNTP

12

Error rate of DNA pol III

Wrong base every 10^5 residues
Exonuclease activity has an error rate of 10^-2
Combined error rate: 10^-7

13

Leading strand vs. lagging strand

Leading strand is constructed as a single sequence
Lagging strand is synthesized discontinuously (Okazaki fragments)
Leading strand is the strand that is synthesized in the same direction as the overall synthesis/unzipping

14

Degradation of RNA primer in Okazaki fragment joining

DNA pol I's exonuclease activity degrades the RNA primer as it moves

15

Cofactor that DNA ligase uses

NAD+

16

Helicases

Unwind double-stranded DNA

17

Topoisomerases

Remove supercoiling ahead of the replisome

18

Single-strand binding proteins

Prevent premature double-helix reformation

19

Differences between replication in prokaryotes and in eukaryotes

1. Okazaki fragments are shorter in eukaryotes
2. Replication rate is slower in eukaryotes
3. Multiple origins of replication in eukaryotes
4. Eukaryotes have at least 5 different DNA polymerases
5. Eukaryotic DNA replication occurs during the S-phase of the cell cycle

20

Sanger sequencing method

DNA replication is performed in presence of ddNTPs
When ddNTP is incorporated into growing strand, synthesis stops (no 3' -OH to add onto)
Gel electrophoresis separates out segments with 1 bp in length difference

21

Only class of cellular macromolecules that has repair mechanisms

DNA

22

Hydrolytic deamination

Common type of DNA damage
Converts cytosine into a uracil residue
Repaired by an excision repair mechanism