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BIOL 207 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

What direction does DNA synthesis proceed in?

A

5’ ⇒ 3’

So new nucleotides are added to the 3’OH end of the primer

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2
Q

Where does the energy for adding nucleotides come from?

A

The hydrolysis/splitting off of pyrophosphate

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3
Q

pyrophosphatase

A

enzyme that splits off more phosphate after the initial cleave & creates more energy

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4
Q

Why can’t DNA polymerases initiate DNA synthesis de novo?

A

They need a preexisting 3’-OH end

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5
Q

Primase

A

RNA polymerase that creates short sequences of RNA called primers

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6
Q

T/F most new strands of DNA initially begins with a primer

A

False

All new strands do

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7
Q

T/F these RNA primers stay in the final product,as they perform the same functions

A

False

They are replaced with DNA

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8
Q

What enzyme replaces RNA primer nucleotides with DNA nucleotides?

A

DNA Pol I (prokaryotes)

Flap endonuclease 1/FEN1 (eukaryotes)

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9
Q

What does dnaB do?

A

Encodes a helicase

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10
Q

Helicase

A

Binds to the origin of replication
Has a pore, which one strand goes through
Unwinds that strand in a 5’ ⇒ 3’ direction

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11
Q

Single Stranded Binding proteins

A

stabilize complex, prevent reannealing of the two strands

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12
Q

What does dnaG do

A

encodes primase

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13
Q

How long are primers?

A

~10 bases

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14
Q

Leading strand

A

The strand that is being synthesized in the same direction as the replication fork.
has continuous synthesis on 3’ end - initially started with a single RNA primer

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15
Q

Lagging strand

A

The strand that is being synthesized in the opposite direction as the replication fork
must be synthesized in okazaki fragments

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16
Q

DNA polymerase III

A

Enzyme that carries out DNA synthesis of long stretches of DNA

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17
Q

Okazaki fragments

A

short discontinuous segments of an RNA primer and replicated DNA

18
Q

How are the rna primers removed?

A

exonuclease activity of DNA Polymerase I

19
Q

How is the gap left by the removed rna primer filled?

A

DNA Polymerase I

20
Q

DNA ligase

A

seals the discontinuous fragments into a single strand

21
Q

Origin of replication

A

specific region of nucleotides that represents where replication begins

22
Q

T/F there is a 5’ overhang left after replication

A

False

It’s a 3’ overhang

23
Q

How many origins of replication are in bacteria

A

One

Synthesis of new strands occurs bidirectionally from two replication forks

24
Q

How many origins of replication are in eukaryotes

A

Many, they are long and not well-defined

25
Q

Describe the origin or replication in bacteria

A

There are AT-rich elements, and sites for DnaA protein to bind to

26
Q

DnaA

A

Bind to the binding sites on orgin of replication and to each other
This bends the dna and separates the AT-rich region

27
Q

How many replication forks are caused by a single origin of replication?

A

Two

28
Q

Topisomerase

A

Relieves pressure on stands caused by helicase untwisting

29
Q

DNA Polymerase III

A

Synthesizes the leading and lagging strands at speeds of 1000 bases/sec

30
Q

B-clamp

A

Keeps Pol III attached to DNA

31
Q

What’s the problem with having linear dna in nucleus?

A

the break at the end would activate the cell repair machinery, that would try and link that linear chromosome to another linear chromosome, which would be lethal

32
Q

What are telomeres

A

long, simple repeat sequences at ends of linear dna

33
Q

WRN protein

A

A part of the telomeric complex

34
Q

Werner Syndrome

A

premature aging caused by impairment of WRN protein in telomeres
Increased occurrence in Japan and Sardinia

35
Q

What does Telomerase do

A

Synthesizes repeat sequences of telomeres

Can bind to and extend these sequences

36
Q

Structure of telomerase

A

multiple subunits and an RNA

37
Q

Describe the RNA in telomerase

A

serves as a template for extending the single-stranded end of a chromosome
150-1300 bases long

38
Q

TERT (Telomerase Reverse Transcriptase)

A

Synthesizes new DNA to complement the RNA in telomerase

39
Q

T/F TERT doesn’t need a 3’OH end to synthesize DNA

A

False

It used the 3’OH end of the 3’ overhang and adds dna nucleotides to the end of that

40
Q

T/F telomerase activity is linked to cancer and aging

A

True

BIOL 207 (6 decks)

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