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molecular cell biology > chapter 5 > Flashcards

chapter 5 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what was griffith’s contribution

A

demonstrated that cells carry a “transforming” molecule

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2
Q

what was avery, mcleod, mccarty’s constribution

A

demonstrated that DNA is the genetic material

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3
Q

what was watson and crick’s contribution

A

double-helix model of DNA
-two strands of DNA are antiparallel and the bases are stacked on one another
-two strands connected by A-T and G-C with 10 base pairs per helix turn

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4
Q

what are the four basic molecular genetic processes

A
  1. transcription
  2. RNA processing
  3. mRNA translation
  4. replication
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5
Q

what is the difference in structure in ribose and deoxyribose

A

in the 2’ position, ribose has an OH

in the 2’ position, deoxyribose has just an H

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6
Q

purines

A

A+G
2 rings

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7
Q

prymidines

A

U+T+C
one ring

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8
Q

what is at the 5’ end of a DNA molecular

A

phosphate group

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9
Q

what is at the 3’ end of a DNA molecule

A

OH group

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10
Q

what are the building blocks of a nucleotide

A

phosphate, sugar, base

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11
Q

what connects nucleotides in a DNA molecule

A

H bond

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12
Q

how can protein interaction bend DNA

A

the conserved C-terminal domain of the TATA box-binding protein (TBP) binds to the minor groove of specific DNA sequences rich in A and T, untwisting and sharply bending the double helix

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13
Q

how can the G+C content of DNA affect the melting temperature

A

the temp at which DNA denatures increases with the proportion of G+C base pairs

the Tm is a function of the G·C content of the DNA; the higher the G+C percentage, the greater the Tm

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14
Q

what does topoisomerase I do

A
  1. relieves torsional stress on DNA
  2. associates with parental DNA strand ahead of the large T-antigen
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15
Q

what did meselson-stahl contribute

A

the idea that DNA replication is semiconservative

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16
Q

what direction is DNA synthesized

A

5’—->3’

17
Q

what are the three requirements for DNA synthesis

A
  1. a primer strand with a free 3’ terminus
  2. a template strand that is base-paired to the primer
  3. a source of dNTPs
18
Q

what is DNA polymerase’s job in DNA synthesis

A

DNA polymerase catalyzes formation of a phosphodiester bond between the 3’ oxygen of the primer stand and the alpha phosphate of a correctly base-paired dNTP

19
Q

what does DNA polymerase I do

A

catalyzed the reaction that adds a single nucleotide to the growing complement strand

20
Q

when a nucleotide is added, what happens

A

two terminal phosphates are cleaved off, released as pyrophosphate

21
Q

what are the general properties of DNA polymerases

A
  1. depend on a single stranded nucleotide
  2. can add free nucleotides ONLY to the 3’ - OH end of an EXISTING polynucleotide (DNA or RNA)
  3. direction of synthesis is 5’ to 3’
22
Q

where does DNA synthesis begin in a bacterial chromosome

A

a site termed the origin of replication

23
Q

how does DNA synthesis proceed in a bacterial chromosome

A

bidirectionally (this results in 2 replication forks)

note: the replication forks eventually meet at the opposite side of the bacterial chromosome, ending its replication

24
Q

how is eukaryotic DNA synthesis different than prokaryotic

A
  1. there is more DNA
  2. the chromosomes are linear
  3. the DNA is complexed with proteins
  4. eukaryotic chromosomes contain multiple origins of replication allowing the genome to be replicated in a few hours
25
Q

what enzyme does proofreading

A

DNA polymerases

note: ALL DNA polymerases have 3’ to 5’ exonuclease activity that allows for proofreading

26
Q

what does helicase (viral large T antigen) do

A

unwinds the parental DNA strands, beginning at a replication origin

27
Q

what does DNA polymerase ε (Pol ε) (epsilon) do

A

extends the LEADING strand up to the replication fork

28
Q

what does PCNA do

A

-sliding clamp

keeps Pol ε stable and associated with the replication fork

forms complexes with DNA Pol ε and Pol δ, preventing dissociation from the DNA template

29
Q

what does RPA do

A

multiple copies of RPA bind the lagging strand (and leading) by keeping it stable and orienting it in the optimal position for replication by Pol δ

binds to single-stranded DNA that has been unwound

maintains ssDNA (single-stranded DNA) template for copying by DNA polymerases

30
Q

what does primase RNA polymerase-DNA polymerase α (Pol α) complex do

A

synthesizes primers for LAGGING STRAND synthesis

31
Q

helicase is what kind of molecule

A

hexamer (6 identical subunits)

32
Q

PCNA–Pol δ complex does what

A

binds the 3’ end of each primer and extends the primer to synthesize most of an okazaki fragment

33
Q

what shape is PCNA

A

donut!

double-stranded DNA passes through the hole in the center

34
Q

what is RFC and what does it do

A

“clamp loader”

binds to PCNA before the “clamp” is opened and opens the ring so that it can encircle a short region of DNA synthesized by Pol α

35
Q

what does the Pol delta RFC PCNA complex do

A

displaces the primase-Pol alpha complex following primer synthesis

36
Q

DNA polymerase alpha is the only polymerase to

A

associate with primase

37
Q

what does DNA polymerase alpha/primase complex do

A

synthesizes a short RNA/DNA hybrid
-10 RNA nucleotides followed by 20 to 30 DNA nucleotides

38
Q

what is the primer synthesized by Pol alpha-primase used for

A

used by DNA polymerase delta or epsilon for the processing elongation of the leading (epsilon) lagging (delta) strands

39
Q

what is polymerase switching and when does it occur

A

the trade-off that occurs when polymerase alpha is done synthesizing the primer

after the RNA-DNA primer hybrid is made, polymerase switching occurs and Pol alpha is replaced by Pol delta (lagging) and Pol epsilon (leading)

molecular cell biology (14 decks)

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