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genetics > genetics chapter 7 part 2 > Flashcards

genetics chapter 7 part 2 Flashcards

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Biology 101 flashcards
1
Q

telomerase is a what?

A

an RNA-dependent DNA polymerase that carries its own RNA template to make new dna sequences

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2
Q

what do most telomeres contain?

A

a knotted fold, or T loop

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3
Q

what are e.coli daughter dna strands synthesized by?

A

dna pol iii holoenzyme

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4
Q

holoenzyme

A

a multiprotein complex where pol iii is associated with the additional components needed for full function

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5
Q

is holoenzyme or replisome bigger?

A

replisome

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6
Q

how does dna polymerase elongate stands of dna?

A

by adding nucleotides to the 3’ end of a pre-existing strand/primer

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7
Q

what are rna primers synthesized by?

A

primase

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8
Q

what has the most fully characterized origin of replication?

A

sacchromyces cerevisiae (yeast)

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9
Q

what are multiple origins or replication called?

A

autonomously replicating sequence (ARS)

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10
Q

topoisomerase

A

catalyze controlled cleavage and rejoining of the dna that prevents over winding and releases torisonal stress

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11
Q

what does DnaA do?

A

binds to the 9-mer sequences, bends DNA, and breaks hydrogen bonds in A-T rich sequences of the 12-mer region

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12
Q

what is DnaB carried by?

A

DnaC

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13
Q

what does dnaC carry?

A

DnaB

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14
Q

what is DnaB?

A

a helicase that uses ATP energy to break hydrogen bonds of complementary bases to seperate the strands and unwind the helix

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15
Q

what keeps the unwinded strands from reannealing?

A

SSB (single stranded binding protein)

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16
Q

what eases a supercoiled DNA?

A

topoisomerase

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17
Q

where is the replisome found?

A

at each replication fork

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18
Q

how many dna pol iii does the replisome carry?

A

2, one for leading strand, one for lagging strand

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19
Q

what 3 activities does DNA pol i use?

A

5’-3’ exonuclease activity to remove the primers
5’-3’ polymerase activity which adds DNA nucleotides to the 3’ end of the preceding DNA segment

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20
Q

what does DNA ligase do?

A

it glues together the okazaki fragments by creating phosphodiester bonds

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21
Q

how many protein subunits does DNA holoenzyme carry?

A

11 and 2 pol iii core polymerases

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22
Q

what are the 2 pol iii core polymerases in the DNA holoenzyme tethered to?

A

Tau protein

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23
Q

what are the tau proteins joined together by?

A

a clamp loader where 2 additional proteins from the sliding clamp

24
Q

why is dna syntheses very accurate?

A

bc dna polymerases have dna proofreading ability

25
Q

dna polymerase enzymes have what type of activity? ?????

A

3’-5’ EXOnuclease activity (reverse synethesis direction)

26
Q

what happens when there is a DNA mismatch?

A

inability of the mismatched bases to form the appropriate h-bonds

27
Q

how is replication in telomeres?

A

leading strand is replicated all the way to the end while the lagging strands need for a primer means that they cannot be completely replicated???

28
Q

what are telomeres?

A

repetiive sequences at the end of the chromosome

29
Q

what do telomeres making sure doesnt happen?

A

makes sure vital genes aren’t affected by incomplete chromosomes

30
Q

what does the T loop in the telomere bind to?

A

the shelterin protein complex

31
Q

what does the shelterin protein complex do?

A

it protects the telomeres from degradation

32
Q

what does telomere shortening eventually trigger?

A

apoptosis

33
Q

what is the hayflick limit?

A

this represents the number of cell cycles before apoptosis occurs

34
Q

what is werner syndrome?

A

early onset aging due to RECQL2 gene encoding a helicase required from telomerase activity

35
Q

what is dyskeratosis congenita?

A

a disorder associated with loss of function of a gene- DKC1 - this gene is supposed to encode a protein needed for normal telomerase function

36
Q

what cells is telomerase normally turned off in?

A

somatic cells

37
Q

What is the most common mutation in cancers of all types?

A

TERT reactivation (this encodes the reverse transcriptase function of a telomerase)

38
Q

what does PCR stand for?

A

polymerase chain reaction

38
Q

what is PCR?

A

an automated version of DNA replication that produces millions of copies of a short target DNA segment

39
Q

what does PCR require?

A

-a double stranded DNA template
-the four dna nucleotides
-a heat stable DNA polymerase
-two different single-stranded dna primers
-a buffer solution

40
Q

what is the most used dna polymerase?

A

taq

41
Q

what is taq isolated from

A

thermus aquaticus

42
Q

what provides the starting point for Taq in PCR?

A

two DNA sequences called PCR Primers

43
Q

what are the three steps of PCR?

A

-denaturation- heated to 95ºC (to denature protein)
-annealing: temp reduced to 45-68º C (allows primer to bind to their complementary sequences in the target DNA)
-extension: temp raised to 72ºC (allows Taq polymerase to synthesize DNA)

44
Q

what is qPCR?

A

a modification to traditional PCR where a spectrophotometer is used to measure DNA production in real time

45
Q

what is the most common detection method for qPCR?

A

SYBR Green

46
Q

what are the benefits of qPCR

A

-can be used to quantitate the starting amount of template DNA accurately
-reduces detection time
-does not require electrophoresis

47
Q

what is ddPCR?

A

the newest version of PCR
that creates thousands of tiny droplets each containing all the components of a PCR reaction
PCR is preformed in each drop
amount of dna per drop is read
results are analyzed

48
Q

what are the benefits of ddPCR?

A

highly quantitative and very sensitive
very good percision

49
Q

what are dNTPs

A

the four standard deoxynucleotide bases

50
Q

what is dideoxy sequencing?

A

it uses DNA polymerase to replicate new DNA from a single-stranded template

51
Q

what is a ddNTP

A

dideoxynucleotide (ddNTP)

52
Q

when does replication cease in sanger sequencing?

A

when a ddNTP is incorporated onto the product DNA molecule

53
Q

what are automated dna sequencers?

A

it uses a single reaction for each DNA sequence where all 4 ddNTPs are included

54
Q

how do they tell the ddNTPs apart?

A

with a fluorescent marker

55
Q

what does the florescent marker do?

A

they each have a different wavelength and a laser light excites the florescent tag on each fragment as it passes. the wavelength is read and information is recorded by a computer

56
Q

how do third generation mothods and Next Generation Sequencing differ from sanger sequencing?

A
  1. tgs and ngs methods use PCR to amplify DNA, this allows feasible sequences of repetitive DNA
  2. tgs and ngs are “massively parallel” this means that millions of sequencing reads may be done in each sequencing run

genetics (23 decks)

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