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BIO 1A03 > T4M2- DNA replication and mitosis > Flashcards

T4M2- DNA replication and mitosis Flashcards

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Biology 101 flashcards
1
Q

what type of structure is DNA present in

A

helical

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2
Q

what types of bonds are present between template strands

A

hydrogen bonding

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3
Q

what type of model is DNA

A

semi conservative

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4
Q

describe the semi conservative model for replication

A

one old and one new strand in each daughter

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5
Q

who demonstrated that DNA replicates in semi conservative manner

A

Matthew Melelson and Frankin Stahl

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6
Q

Describe Melelson and Stahl’s experiment

A

Cultured e coli bacteria cells for generations with nucelotide precursers with N15
- transferred bacteria to medium with N14
- extracted samples and centrifuged to separate DNA based on density

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7
Q

Where was the band on the N15?

A

sat lower due to heavy density

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8
Q

where was the N14 band?

A

sat higher due to lower density

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9
Q

what model was ruled out

A

conservative model

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10
Q

in what direction is the template strand copied

A

3’ to 5’

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11
Q

in what direction does DNA synthesis occur

A

5’ to 3’

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12
Q

what type of bonding is in between complementary nucleotides

A

hydrogen bonding

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13
Q

what does the incoming nucleotide interact with

A

3’ hydroxyl of polymer

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14
Q

what type of bond forms between new daughter strand and incoming nucleotide

A

phosphodiester bond

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15
Q

where does unwinding occur and what does it separate

A

the separation of the parent strands at replication fork within origin of replication

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16
Q

what does initiation require and why

A

short RNA primer- to synthesize and base pair with template DNA

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17
Q

what enzyme catalyzes the polymerization of each daughter strand

A

DNA polymerase

18
Q

describe the leading strand

A
  • continuous
  • needs only one primer and DNA polymerase can add nucleotides to new daughter cell
19
Q

describe the lagging strand

A
  • anti parallel
  • has fragmented or discontinuous DNA
20
Q

in which direction does DNA synthesise in lagging strand

A

5’ to 3’

21
Q

what is formed along the lagging strands

A

okazaki fragments formed by separate primers

22
Q

what enzyme binds to parental DNA to initiate unwinding of double helix

A

DNA helicase

23
Q

what does DNA helicase do

A

breaks hydrogen bonds between base pairs

24
Q

what stabilizes DNA from rejoining after unwinding

A

single stranded binding proteins

25
Q

describe the function of topoisomerase

A

binds upstream replication fork to ease tension produced at unwinding

26
Q

role of RNA primase

A

synthesizes short RNA stretches of nucleotides complementary to parental strands

27
Q

role of DNA polymerase iii

A

does most of elongation work in prokaryotes

28
Q

role of DNA polymerase i

A

removes primer after RNA primer and replaces with nucleotides

29
Q

how many origins of replication are in prokaryotes

A

one region of replication

30
Q

what does DNA ligase do

A

joins 3’ end of fragment to adjacent DNA nucleotide by catalysing phosphodiester bond, forming okazaki fragments

31
Q

what happens if the wrong nucleotide is added during replication

A

DNA polymerase replaces it

32
Q

how does replication occur in prokaryotes

A

at one site of replication- and continues in circular chromosome

33
Q

what way is elongation

A

5’ to 3’ end

34
Q

why can RNA primer on lagging strand not be replaced with DNA nucleotides

A

no 3’ end available

35
Q

what is present at the end of linear chromosomes

A

telomers

36
Q

define telomeres

A

special sequences made of repetitions of one short nucleotide sequence

37
Q

what is the telomere sequence

A

TTAGGG

38
Q

what happens to the telomere sequence through times of replication

A

gets shorter and is used as a buffer to protect DNA- very short for the elderly

39
Q

does telomere shortening affect gametes or stem cells?

A

no- they have telomerase enzyme to catalyze lengthening

40
Q

what enzyme is a reverse transcriptase?

A

telomerase

41
Q

what type of protein is telomerase

A

ribonucleic protein

42
Q

where is DNA replicated

A

ori sites

BIO 1A03 (10 decks)

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