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Genetics > ch 7 DNA structure and replication > Flashcards

ch 7 DNA structure and replication Flashcards

1
Q

4 biological macromolecules

A
  • polysaccharides
  • nucleic acids
  • lipids
  • proteins
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2
Q

rough strain of S. pneumoniae

A
  • lacks a polysaccharide coat
  • avirulent (non-disease causing)
  • immune system can detect and therefore destroy
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3
Q

smooth strain of s. pneumoniae

A
  • has a polysaccharide coat
  • virulent (disease causing)
  • immune system can’t recognize cell because of the slime layer
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4
Q

Griffith experiment conclusion

A

a non-living substance is responsible for transforming avirulent R-strain into virulent S-strain

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5
Q

Avery, MacLeod, McCarty experiment

A

eliminated different compound of hear killed S strain
- only elimination of DNA caused elimination of transforming ability

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6
Q

Hershey and Chase expreiment

A

used radioactive labels to label T2 phage components
- hereditary compound must be injected into the host
35S - protein specific (proteins get labelled); liquid (supernatant) will be radioactive
32P - nucleic acid specific (nucleic acid gets labelled); cell pellet will be radioactive

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7
Q

3 pieces of info Watson and Crick discovered

A
  1. DNA is composed of 4 nucleotides
  2. Rules for nucleotide composition
  3. helical in structure
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8
Q

purines

A

adenosine
guanine

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9
Q

pyrimidines

A

cytosine
thymine

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10
Q

nucleoside

A

a molecule composed of a nitrogen base bound to a sugar molecule

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11
Q

nucleotide

A

a molecule composed of a nitrogen base, a sugar, and a phosphate group; the basic building block of nucleic acids

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12
Q

semiconservative replication

A

a model of DNA replication in which each strand of parental DNA serves as a template for new DNA synthesis resulting in both daughter molecules being composed of one parental and one newly synthesized strand

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13
Q

conservative replication

A

a model of DNA replication which predicts that half of the daughter DNA molecules should have both strands composed of newly polymerized nucleotides
- disproved

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14
Q

dispersive replication

A

a model of DNA replication which predicts the more or less random interspersion of parental and newly synthesized segments in daughter DNA molecules

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15
Q

Meselson and Stahl experiment

A
  • labeled parental DNA by growing E. coli in 15N medium for many generations
  • transferred to 14N medium
  • extract DNA after the 1st and 2nd generations
  • centrifuged the DNA in a CsCl gradient to separate DNA of different intensities
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16
Q

origin of replication

A

the start point of DNA replication
- recognition sequence with an associated AT rich region

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17
Q

DnaA

A

protein which binds to DnaA boxes and opens the helix

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18
Q

DnaB

A
  • helicase
    protein which binds to the ssDNA created by DnaA, continues to open the helix
  • directional slides 5’ to 3’
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19
Q

single-stranded binding proteins

A

SSBs
bind to open helix, keep strands apart

20
Q

replication fork

A

the point at which the two strand of DNA are separated to allow for the replication of each strand

21
Q

DNA polymerase III

A

adds nucleotides to the 3’ OH (complementary to the parental)

22
Q

leading strand

A

the DNA strand that is being synthesized in the same direction as the replication fork is proceeding

23
Q

lagging strand

A

the DNA strand that is being synthesized in the opposite direction as the replication fork is proceeding

24
Q

okazaki fragments

A

a small segment of single stranded DNA, with a RNA primer at the 5’terminus, synthesized as part of the lagging strand during DNA replication

25
Q

DNA polymerase I

A

degrades RNA, fills in with DNA

26
Q

4 steps of synthesis on lagging strand

A
  1. primase synthesizes short RNA oligonucleotides (primer) copied from DNA
  2. DNA polymerase III elongates RNA primers with new DNA
  3. DNA polymerase I removes RNA at 5’ end of neighboring fragments and fills gap
  4. DNA ligase connects adjacent fragments
27
Q

ligase

A

links DNA fragments by forming the phosphodiester bond

28
Q

topoisomerases

A

relieves the strain created from unwinding the DNA helix

29
Q

3 steps to remove strain from unwinding

A
  1. DNA gyrase cuts DNA strands
  2. DNA rotates to remove the coils
  3. DNA gyrase rejoins the DNA strands
30
Q

unwinding components:

A

helicase - strand separation
topoisomerase - strain relief
SSBs - keeps helix open

31
Q

catalytic components:

A

2 associated polymerase III’s (dimer)
Beta clamp for processivity
primase for lagging strand synthesis

32
Q

okazaki fragment components:

A

DNA polymerase I
DNA ligase

33
Q

replisome

A

responsible for DNA replication

34
Q

overall DNA replication error rate

A

10^-10

35
Q

exonuclease subunit of polymerase III

A

recognizes mispairings (proofreading), removes the incorrect nucleotide and replaces it

36
Q

DNA polymerase III is capable of adding

A

1000nt/sec

37
Q

eukaryotic differences from prokaryotes

A
  • genomes are much larger
  • replication is restricted to S phase
  • chromosomes can only be replicated once
  • chromosomes are comprised of chromatin (DNA and histones)
  • chromosomes are generally linear
38
Q

origin recognition complex (ORC)

A

binds to the origin (box element)

39
Q

Cdc6 and Cdt1

A
  • binds to ORC at the origin
  • recruits the helicase
  • regulates replication
40
Q

helicase

A

separates DNA helix
inhibited by Cdc6 and Cdt1

41
Q

regulation of replication

A

M: synthesis of Cdc6 and Cdt1
G1: pre-replication complex forms (ORC, Cdc6, Cdt1, and helicase (inactive))
right before S: Cdc6 and Cdt1 degraded and complex becomes active

42
Q

telomere

A

the tip/end of a linear chromosome

43
Q

telomere problem

A

for linear eukaryotic chromosomes, removal of the last primer of the lagging strand leaves a gap
- chromosomes would get shorter with each replication
- unable to add nucleotides due to lacking a 3’ OH

44
Q

telomere solution

A

telomerase (RNA protein hybrid enzyme) adds repeated DNA sequence to 3’ end using a RNA template
- provides a buffer zone for shortening

45
Q

steps in lengthening the 3’ overhang

A
  • telomerase RNA acts as a template
  • reverse transcriptase activity (DNA from RNA template)
  • repetitive sequence allows repositioning that creates buffer that can be lost
46
Q

werner syndrome and dyskeratosis congenita

A

deficiencies in telomerase

47
Q

senescence

A

germ line cells have high activity of telomerase while somatic cell have lower activity
- deterioration with age

Genetics (9 decks)

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