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AP BIO > DNA Replication > Flashcards

DNA Replication Flashcards

1
Q

what were the experimental organisms that enabled scientists to learn about DNA?

A

bacteria and viruses

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2
Q

what did Griffith work with in 1928?

A

bacteria that causes pneumonia

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3
Q

what 2 strains did Griffith work with?

A

S (smooth) Strain - encased in a capsule and pathogenic

R (rough) Strain - lacked a capsule and could be destroyed by the host’s immune/lymphatic system

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4
Q

What happened in the experiment where heat killed S cells were mixed with R cells?

A

DNA from the heat killed S was picked up by the living R and they “transformed” into pathogenic S cells

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5
Q

what did Griffith’s experiment show?

A

transformation - when DNA from one source assimilates into another source, causing a change/ “transformation” in genotype and phenotype

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6
Q

who was the first to suggest that DNA was the agent being transferred between bacteria cells?

A

Oswald Avery

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7
Q

what did most scientists think were the agents?

A

proteins

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8
Q

what are phages?

A

viruses that infect bacteria

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9
Q

who proved that it was DNA and not proteins that were responsible for transferring genetic info ? through what work?

A

Hershey and Chase; through their work with bacteriophages

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10
Q

what are bacteriophages?

A

viruses that infect bacteria

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11
Q

at minimum, what is a virus?

A

DNA/RNA in a protein coat called a capsid

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12
Q

protein contain what elements?

A

CHON

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13
Q

what is different between proteins and DNA?

A

protein - S
DNA -P

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14
Q

what did batch 1 have?

A

radioactive S (protein)

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15
Q

what did batch 2 have?

A

radioactive P (DNA)

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16
Q

what was incorporated in T2 bacteriophages that infect E coli bacteria?

A

2 different radioactive tags - S and P

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17
Q

what was the result of Hershey and Chase’s experiment?

A

P appeared in E coli and S didnt, so DNA was being transferred

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18
Q

who noticed the percentages of A,T,C,G in DNA?

A

Chargaff
A and T ~ 30%
C and G ~ 20%

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19
Q

A=T and C=G equalities are known as

A

Chargaff’s Rule

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20
Q

the race to discover DNA’s true shape was won by?

A

Watson and Crick
(Maurice Wilkins also won Nobel Prize)

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21
Q

how was DNA’s shape found?

A

Rosalind Franklin took X-ray crystallography images taken, and Watson and Crick saw that it was a double helix

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22
Q

the correct model of DNA consists of

A

sugars (deoxyribose) and phosphates along the sides of the ladder and the N bases along the rungs

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23
Q

bonds between phosphate group and sugar?

A

covalent phosphodiester

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24
Q

bonds between complementary n bases?

A

H bonds

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25
Q

bonds bw non complementary n bases?

A

Van der Waals

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26
Q

how many bonds bw adenine and thymine?

A

2

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27
Q

how many bonds bw cytosine and guanine?

A

3

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28
Q

what needs to happen before DNA copies itself?

A

H bonds bw the nitrogen bases must be broken first

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29
Q

what does a template (old) strand act as?

A

acts as a guide for the formation of a new complementary strand

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30
Q

what happens in DNA replication?

A

nucleotides - simple sugar deoxyribose, phosphate group, and a nitrogenous base- line up along the template strand according to base pairing rules

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31
Q

where are the two old strands located in replication?

A

outside

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32
Q

where are the two new stands located in replication?

A

inside

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33
Q

when a double helix duplicates, what is the resulting daughter molecules?

A

2 new helices, with one new and one old- semiconservative model

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34
Q

why was DNA replication first studied in E coli?

A

they have a single circular chromosome called the nucleoid (5 million base pairs) and can undergo DNA replication in less than an hour

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35
Q

how is DNA replication in humans?

A

46 chromosomes - 6 billion base pairs
takes a few hours to replicate and divide

36
Q

how much is known about DNA replication in prokaryotes than eukaryotes?

A

a lot more is known

37
Q

in prokaryotes, where does DNA replication begin?

A

origin of replication and it proceeds in both directions along the circular DNA molecule until entire molecule is copied

38
Q

how is DNA replication in eukaryotes?

A

linear and there are 100-1000’s of origins of replications

39
Q

why do eukaryotes have many origins of replciation?

A

increase speed of copying very long DNA strands

40
Q

the opening of 2 strands of DNA does what?

A

creates bubbles that eventually fuse together forming 2 daughter DNA strands

41
Q

what is the point where bubbles formed called?

A

replication fork

42
Q

who adds nucleotides to the DNA strand?

A

DNA polymerase

43
Q

where does the energy to add nucleotide come from?

A

nucleoside triphosphate- nucleotides but with 3 phosphate groups instead of 1

44
Q

how does nucleoside triphosphate provide energy?

A

very negatively charged and unstable, which accounts for the exergonic energy involved to drive reactions

45
Q

what is the structure of 2 DNA strands?

A

antiparallel

46
Q

what does antiparallel mean in terms of DNA?

A

their sugar-phosphate backbones run in opposite directions

47
Q

5’ end

A

phosphate group

48
Q

3’ end

A

hydroxyl group

49
Q

with DNA replication, in which direction does the growing strand grow?

A

5’ to 3’

50
Q

when DNA molecule opens up for replication, which what direction does it grow off from?

A

3’ to 5’ from the template strand

51
Q

which direction does the daughter strand always grow in?

A

5 to 3

52
Q

leading strand

A

complementary strand of new DNA

53
Q

overall direction of the DNA replication in replication forks opening left?

A

towards the left

54
Q

creating fragments in 5’ to 3’ direction

A

backstitching

55
Q

lagging strand

A

DNA polymerase builds new DNA in 5 to 3 direction, and in a direction opposite to the leading strand and in short segments

56
Q

short segments of DNA in lagging starnd

A

Okazaki fragments

57
Q

how are Okazaki fragments linked?

A

enzyme DNA ligase

58
Q

in a bubble, what are the leading and lagging strands?

A

leading strand - top left, bottom right
lagging strand - top right, bottom left

59
Q

all replication bubbles fuse to form…

A

two new strands of DNA on the inside

60
Q

which enzyme adds nucleotides before DNA polymerase?

A

primase

61
Q

in what direction does primase add nucleotides?

A

5’ to 3’

62
Q

are the nucleotides added by primase DNA or RNA?

A

RNA

63
Q

what is the resulting RNA fragment added by primase called?

A

RNA primer

64
Q

which enzyme replaces RNA primer?

A

2nd diff DNA polymerase (I)

65
Q

what is the first step of DNA replication?

A

DNA helicase breaks the H bonds to unzip and unwind the double helix

66
Q

what happens after DNA unwinds due to helicase?

A

single strand binding proteins hold open the unwound DNA molecule

67
Q

what does topoisomerase do?

A

helps relieve tension created by unwinding DNA

68
Q

what does primase do after SSBP attach?

A

arrives to prime/start building the daughter strand, adding about 10 RNA nucleotides in a 5’ to 3’ direction

69
Q

what happens once RNA nucleotides are added?

A

DNA polymerase (III) adds complementary DNA nucleotides
DNA polymerase (I) replaces RNA primer with DNA

70
Q

last enzyme involved in DNA replication

A

DNA ligase
links Okazaki fragments in lagging strand

71
Q

how rare are errors in matching base pairs?

A

one error per billion

72
Q

what proofreads mistakes that are made in DNA replication?

A

DNA polymerase
it immediately replaces a nucleotide if the wrong one is added and resumes replication

73
Q

what causes mutations to existing DNA?

A

chemicals, radioactivity, UV light, X rays

74
Q

what correct damaged DNA?

A

repair enzymes

75
Q

what does nuclease do?

A

cuts out damaged DNA segment and DNA polymerase fills the gap and DNA ligase seals it up

76
Q

what enzymes replace the last fragment of the DNA molecule?

A

no enzymes can do that

77
Q

since last fragment of DNA is not replaced, what happens after repeated replication?

A

shorter and shorter DNA molecules are produced

78
Q

what solves the problem or DNA molecules getting shorter?

A

eukaryotes have telomeres on the ends of their DNA

79
Q

telomeres?

A

segments at the end of a DNA molecule that do not contain genes, so therefore do not make proteins

80
Q

what sequence are telomeres?

A

TTAGGG

81
Q

what do telomeres protect?

A

the organism’s genes/DNA from being eroded away through successive rounds of DNA replication

82
Q

because of telomeres, how are our genes that code for traits?

A

unaffected until we’re older as the telomeres shorten instead

83
Q

what does enzyme telomerase do?

A

helps lengthen the telomere ends

84
Q

where is telomerase present?

A

in germ line cells that form eggs andsperm

85
Q

what are scientists questioning about the relationship between life span and telomeres?

A

if an organism’s life span is limited by the length of telomeres

86
Q

what is the downfall of adding telomerase to somatic cells?

A

increases risk of cancer

AP BIO (30 decks)

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