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Bio 2 > DNA replication > Flashcards

DNA replication Flashcards

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Biology 101 flashcards
1
Q

What is helicase?

A

It unwinds parental double helix at replication forks

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2
Q

What is a single-strand binding portein

A

It binds to and stabilizes the single stranded DNA until it is used as a template

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3
Q

What is topoisomerase

A

it relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA

prevent supercoiling

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4
Q

what is primase

A

it synthesizes an RNA primer at the 5’ end of the leading strand and at the 5’ end of each Okazaki fragment of the lagging strand

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5
Q

What does DNA pol III do

A

it synthesizes a new DNA strand by adding nucleotides to an RNA primer

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6
Q

what does DNA pol I do

A

it removes the RNA nucleotides from the primer at the 5’ and replaces then with DNA nucleotides

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7
Q

What is DNA ligase

A

it joins okazaki fragments on the lagging strand

it joins the 3’ of DNA that replaces primer to rest of leading strand

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8
Q

What are Okazaki fragments

A

short sections of DNA that are synthesized on the lagging strand of the replicating DNA

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8
Q

What is the replication fork

A

the open section of DNA where DNA pol III can replicate the parent strand

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9
Q

What is DNA pol

A

an enzyme that replicates DNA

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10
Q

what is the leading strand

A

the new DNA strand that continiously grows in the 5’-3’ direction

it requires one primer

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11
Q

features of leading strand

A

one primer needed

daughter strand elongates towards the replication fork

made continuously

synthesized in 5’-3’

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12
Q

features of lagging strand

A

made in segments

daughter strand elongates away from the replication fork

multiple primers are needed

synthesized in the 5’-3’ direction

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13
Q

How does the lagging strand get analyzed and fused?

A
  1. DNA pol III binds to 3’ end of RNA primer
  2. DNA pol synthesizes in 5’-3’ direction until it reaches the previous RNA primer
  3. DNA pol III falls off and is replaces by pol I
  4. pol I removes each RNA nucleotide on primer and replaces with DNA
    Step 2: DNA pol III falls off and is replaced by DNA pol I.
  5. when it reaches the 5’ end of next fragment, it falls off and DNA ligase closes the gap between the two
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14
Q

What provides energy for the addition of a new nucelotide?

A

Release of pyrophosphate from the incoming nucleotide, and then hydrolysis of the pyrophosphate to inorganic phosphate

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15
Q

what is the semi conservative model of replication

A

two identical DNA double helices are formed from replication, each with one parent strand and one daughter strand

16
Q

what are the three requirements of replication

A

parental DNA molecule, Enzymes, Nucleotide triphosphates

17
Q

what is the difference in origin of replication for bacteria and eukaryotes?

A

bacteria have single origins of replication while eukaryotes have many

18
Q

what direction does replication occur from the origin

A

both directions until entire molecule is copied

19
Q

what can DNA polymerase not do?

A

initiaite synthesis, it can only add to an existing 3’OH end

20
Q

What is the purpose of RNA primase

A

it can start an RNA chain from scratch and provide a 3’OH starting point for the DNA pol

21
Q

what does DNA pol III do

A

synthesizes a new DNA strand by covalently adding nucleotides to the 3’ end of a pre-existing DNA strand or DNA primer

22
Q

what does DNA Pol I do

A

It removes RNA nucelotides of a primer from the 5’ end and replaces them with DNA nucleotides

23
Q

What are the 3 common features of DNA pol

A

Add new bases to 3’ end of strands

synthesize in 5’3’ direction

require and RNA primer

24
Q

How is energy provided for nucleotide additions

A

dATP supplies adenine to DNA and as each monomer is added, it loses two phosphate groups as a molecule of pyrophosphate

25
Q

Centromere

A

the constricted waist of chromosomes where kinetochores assemble

26
Q

What are kinetochores?

A

Protein complexes that assemble at centromeres of chromosomes

they serve as attachment sites for microtubules in cell division

27
Q

What is cohesion in chromosomes?

A

proteins that join sister chromatids together during mitosis.

The cleavage of this triggers anaphase

28
Q

Before replication, each chromosome is composed of:

A

a single DNA molecule

29
Q

What does DNA ligase do specifically

A

it makes the final phosphodiester bond at each “nick” between the 3’-OH of the DNA replacement nucleotides (DNA pol I removed primer) and the 5’ end of the DNA pol III strand

30
Q

Which phase is a cell in most of the time?

A

interphase

31
Q

after replication, each chromosome is composed of

A

2 identical DNA molecules

32
Q

What are the replicated chomosomes called and how are they held together?

A

They are called sister chromatids and are held together at their centromeres by cohesion proteins.

Bio 2 (16 decks)

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