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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
DNA polymerase I
degrades RNA, fills in with DNA
26
4 steps of synthesis on lagging strand
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
ligase
links DNA fragments by forming the phosphodiester bond
28
topoisomerases
relieves the strain created from unwinding the DNA helix
29
3 steps to remove strain from unwinding
1. DNA gyrase cuts DNA strands 2. DNA rotates to remove the coils 3. DNA gyrase rejoins the DNA strands
30
unwinding components:
helicase - strand separation topoisomerase - strain relief SSBs - keeps helix open
31
catalytic components:
2 associated polymerase III's (dimer) Beta clamp for processivity primase for lagging strand synthesis
32
okazaki fragment components:
DNA polymerase I DNA ligase
33
replisome
responsible for DNA replication
34
overall DNA replication error rate
10^-10
35
exonuclease subunit of polymerase III
recognizes mispairings (proofreading), removes the incorrect nucleotide and replaces it
36
DNA polymerase III is capable of adding
1000nt/sec
37
eukaryotic differences from prokaryotes
- 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
origin recognition complex (ORC)
binds to the origin (box element)
39
Cdc6 and Cdt1
- binds to ORC at the origin - recruits the helicase - regulates replication
40
helicase
separates DNA helix inhibited by Cdc6 and Cdt1
41
regulation of replication
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
telomere
the tip/end of a linear chromosome
43
telomere problem
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
telomere solution
telomerase (RNA protein hybrid enzyme) adds repeated DNA sequence to 3' end using a RNA template - provides a buffer zone for shortening
45
steps in lengthening the 3' overhang
- 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
werner syndrome and dyskeratosis congenita
deficiencies in telomerase
47
senescence
germ line cells have high activity of telomerase while somatic cell have lower activity - deterioration with age

Genetics (9 decks)

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