EXAM2_L14_DNA_Replication Flashcards Preview

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Flashcards in EXAM2_L14_DNA_Replication Deck (21)
1

Replication reminders

1. duplicates entire genome
2. once per cell cycle
3. semi-conservative
4. bi-directional replication until rep forks collide or end of chromosome reached
5. semi-discontinuous (lagging strand)

2

Mechanism of replication 1,2,3.

1. Initiation (proteins bind to DNA, open helix, prepare DNA for base pairing)
2. Elongation (proteins connect nucleotides into continuous new DNA strand)
3. Termination (proteins release replication complex)

3

Origins of replication- structure, proteins used, function.

Multiple origins in DNA w/ TATA rich sequences.
Origin binding proteins separate DNA forming a replication bubble where other proteins recruited to replicate DNA

4

DNA Helicase- function

unwinds and extends replication fork in 5'to3' direction respective of leading strand.
- Req ATP

5

SSBP- funciton

binds ssDNA to prevent strands from reattaching after helicase unwinds the DNA.
- prevents DNA degradation
-binds cooperatively
-NOT ENZYMES

6

two ways of orienting 5' to 3'

Growth of new daughter strand is always 5' to 3'
or
Growth always occurs toward the 5' end of the Parent strand

7

what are 4 components req for replication?

1. dNTPs
2. ssDNA template
3. a free 3' OH group
4. RNA primer (b/c dna pol cant make strands denovo)

8

7 proteins of replicaiton

1. Helicase
2. SSB
3. Primase
4. DNA Pol
5. RNase H
6. DNA ligase
7. Topoisomerase

9

What drives replication?

ATP and energy from phosphates on nucleotides.
-Makes it almost irreversible reaction

10

Three rules for DNA Polymerase. Types of DNApol?

1. copy ssDNA
2. add bases ONLY to existing chains (base pairing)
3. ONLY extend from 5' to 3' direction
-alpha, epsilon, gamma (major replicative DNApol)

11

How does replication get started?

Primase makes RNA primer
-primer makes short dsRNA base-paired to DNA template with 3'-OH
-DNApol starts
-RNA portion removed/replaced with DNA later

12

Inhibition of DNA synthesis (types,examples,mech)

-Nucleoside analogs
NRTI- nucleoside reverse transcriptase inhibitor (anti-HIV)
-ie-ddl, ZDV
Have no 3' carbon OH so no elongation occurs

13

DNA Pol alpha

proofreads/ manages replication

14

RNase H

-recognizes RNA-DNA duplexes and removes the primer, leaving the DNA part intact

15

Two nicks

1. between okazaki fragments
2. between colliding replication forks
important for DNA to identify new daughter strand when repairing

16

How are okazaki fragments numbered?

first fragment is #1 and counts up to the newest fragment.

17

Topoisomerase

Supercoil unwinding ahead of helicase.
Type 1 cuts ONE strand
Type 2 cuts BOTH strands

18

What are two topoisomerase inhibitors for type 1 and 2? Why used? 2 modes?

Camptothecin Topoisomerase I inhibitor
Doxorubicin Topoisomerase II inhibitor
-cancer Chemotherapeutic agents
1. prevent unwinding
2. prevent re-sealing
both cause cell death

19

Telomeres structure funciton

end of linear chromosome
-ds and ss DNA
-composed of thousands of repetitive sequence of non-coding DNA
-Protects DNA from damage
"TTAGGG"

20

End-replication problem. How solved?

-successive rounds of DNA replication on lagging strand will produce daughter strands that are progressively shorter
When final RNA primer (lagging strand) removed, there is no way to replace it with DNA
TELOMERASE FIX!

21

Telomerase

contains RNA template used to extend the parental DNA template.
-RNA-dep DNA polymerase (ribonucleoprotein)
Uses its own RNA template to make DNA instead of using the RNA left from RNA primer removal.
-Chromosomal end of DNA and telomerase RNA are complementary ie: telomere seq 5'-TTAGGG-3', Telomerase 5'-CCCUAA-3'