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Molecular > Lect 3 > Flashcards

Lect 3 Flashcards

1
Q

Central dogma DNA to…to..

A

DNA
RNA protein

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2
Q

Importance of replication

A

Providing genetic info needed by daughter cells
Doubling cells content before division during S phase

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3
Q

Replication process is

A

Semi conservative

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4
Q

DNA polymerase is… Enzyme
Function
Steps

A

Template directed
Catalyse formation of polypeptide chain by adding nucleotides from dNTPs

  1. H bond , base complementation
  2. Pyrophosphate removal
  3. Formation of phosphodiester bond
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5
Q

DNA pol synthesis vs read
Requires

A

5’ to 3’
3’ to 5’
RNA primer with free 3’ OH

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6
Q

DNA ligase func
Requires

A

Joins 2 DNA segments by catalyzing the formation of phosphodiester bonds

NAD + prokaryotes
ATP eukaryotes

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7
Q

DNA helicase func
Requires

A

Unwinds the double helix of DNA
ATP

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8
Q

During DNA strand unwinding…occurs which requires….

A

Supercoiling
Topoisomerase enzyme

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9
Q

Topoisomerase types comparison

A

1, cuts a nick in 1 strand only allowing rotation and bond reformation afterwards

2, transient break in both strands then reseals the bond, needs ATP, can introduce -ve supercoils

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10
Q

Gyrase

A

In E.coli can
Introduce -ve supercoils
Separate interlocked DNA molecules after replication

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11
Q

inhibitors

A

Quinolones> like tarivid and ciprobay, antibiotic inhibits DNA gyrase
Teniposide and doxorubicin> antitumor drug inhibits type 2 topoisomerase

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12
Q

Replication fork
Prepriming complex componenets

A

V shape and bidirectional
DNA a and DNA B and DNA c bindi g to the ORI c and SSB

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13
Q

Ori C is rich in …why

A

A–T bonds as only 2 hydrogen bonds present so easier to break

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14
Q

Dna A
Dna B
Dna C
SSB

A

Produces local opening and unwinding of DNA double helix at Ori C requiring ATP
Also a type of helicase that req ATP
Binds to Ori C
Single strand binding proteins, stabilise single strands and protect from nucleases action

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15
Q

Replication fork is created by the action of…. and…

A

Helicase
SSB proteins

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16
Q

How SSB proteins bind
Their absence

A

Cooperatively one molecule makes it easier for the rest
Rewinding of DNA again

17
Q

Initiation phase
Both strands act as…
RNA primer is….bp formed by…reads from and synthesis
Adds nucleotides from
Primase and prepriming complex form…

A

Template
5
Primase enzyme, DNA dependent RNA polymerase
3’ to 5’
5’ to 3’
NTPs (ATP/GTP/UTP/CTP)
Primosome

18
Q

Steps of primase action

A
  1. 2 NTPS form H bonds with first 2 nucleotides of template strand
  2. Loss of pyrophosphate
  3. Formation of phosphodiester bond
  4. 3’OH is free as primase moves to 5’ end and another nucleotide is added
19
Q

Why DNA polymerase do not initiate synthesis of DNA

How start

A

As the proofreading of the first few nucleotides is not accurate

Adds to 3’OH

20
Q

Elongation by…
Synthesises …adds nucleotides….from…

A

DNA polymerase III
Both strands
One at a time
dNTPs

21
Q

Rate of chain elongation is…..per second
It is highly…….synthesising…… In one cycle

A

20-50
Processive
50000

22
Q

The number of nucleotides added to the Nascent chain before the polymerase disengages from the templates

A

Processivity

23
Q

The 2 newly synthesised strands grow….

One leading
The other lagging

A

In opposite directions
one continuously towards and one discontinuously away from the replication fork

24
Q

Lagging strand formed in pieces abt…….to…called…

A

1000-2000
Okazaki fragments

25
Q

DNA synthesis is…..
On leading only one…is needed
On lagging ….

A

Semi discontinuous
RNA primer
Many RNA primers

26
Q

Pol III has….activity that removes misplaced nucleotides by….

A

Proof reading
Exonuclease

27
Q

Pol II

A

Repair and proofread

28
Q

Pol I

A

Removes RNA primers 5’ to 3’ exonuclease activity
Fills gaps 5’ to 3’ by polymerase activity
Proofreads 3’ to 5’ exonuclease activity
Repair

29
Q

After bacterial DNA replication the result is 2 double stranded circular DNA molecules interlocked together fixed by

A

Topoisomerase II

30
Q

What ensures high processivity for pol III

A

B subunit of DNA pol III in E.coli

Molecular (6 decks)

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