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PHYS 395 > Chapter 5: Photochemistry and Radiation Chemistry of DNA damage, Molecular Mechanisms of DNA damage > Flashcards

Chapter 5: Photochemistry and Radiation Chemistry of DNA damage, Molecular Mechanisms of DNA damage Flashcards

1
Q

Humans have ______ cells, typical cell size _______ and typical cell mass ______.

A

10^14
10 um
1 ng

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2
Q

DNA is ___________, RNA is ___________.

A

hereditary material of genes
information necessary to build proteins/enzymes.

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3
Q

________ is the principle target for the biological effects of radiation including __________, ___________, and __________.

A

DNA
cell killing
carcinogenesis
mutation

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4
Q

Minor grooves of DNA are _________, major grooves are _________ and width of DNA is __________.

A

1.2 nm
1.8 nm
2 nm

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5
Q

The purines are DNA bases ___________ and have ________.
The pyrimidines are DNA bases ____________ and have ________.

A

adenine and guanine
2 ring
cytosine, thymine and uracil
1 ring

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6
Q

A nucleotide is made up of __________ covalently linked to __________. Nucleotides are covalently linked together in ______________.

A

sugar-phosphate
base
polynucleotide chains

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7
Q

Because the _____________ is different, we can determine the purity of DNA samples.

A

absorption spectrum of proteins

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8
Q

A sample of DNA should have ratio A260nm : A280nm equal to ____________ if it is _______.

A

1.6 - 1.8
pure
????? should it be 0.16-0.18????

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9
Q

The absorption of DNA is due to _________. Because ________ has the lowest triplet state it is the ______________.

A

bases
thymine
primary candidate for photo-induced changes

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10
Q

UV exposure in wavelength range ________ affects ________, _________ are not directly altered.

A

bases
sugar-phosphate

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11
Q

The 7 main products found in DNA after absorption of UV at 254 nm are: ___________.
The most important/highest in quantity is __________.

A
  1. pyrimidine dimers
  2. hydrates
  3. DNA protein crosslinks
  4. spore photoproducts
  5. 6-4 pyrimdine adducts
  6. thymine glycole
  7. strand breaks
    pyrimidine dimers
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12
Q

Absorption of thymine dimer is __________, absorption of irradiated thymine is ________ and absorption of unirradiated thymine is _________.

A

lowest, medium, high

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13
Q

The excitation energies of singlet states for bases is _________ than the excitation energies of triplet states for bases . ________ has the lowest energy.

A

higher
thymine

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14
Q

Pyrimidine dimes are chemically __________ and can survive ____________.

A

extremely stable
acid hydrolysis of DNA

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15
Q

Hydrates are formed by __________ at ________. They are _________ and ___________.

A

water addition
5-6 double bond of pyrimidine bases
unstable
revert easily with changes in pH or temperature

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16
Q

WRT yield of pyrimidine dimers in mammalian cells __________ has highest yield, then ________, then _________.

A

6-4 product
protein crosslinks
SSB

17
Q

6-4 pyrimidine addect has _________ yield than dimers and __________ and may be more important for ___________.

A

smaller
contributes to lethality
mutations

18
Q

The 3 classes of compounds that play a role in photosensitization of DNA are __________, __________, and ___________.

A

halogenated pyrimidines
ketones
furocoumarines

19
Q

The main halogenated pyrimidine is ___________/____________. It changes the absorption spectrum by __________. Exposure to _________ excites the _________ ultimately leading to ___________.

A

bromouracil/nucleoside bromodeoxuridine
extending it to longer wavelengths
313 nm
bromouracil
single strand break

20
Q

The ketones with sensitizing action are _________, __________, and _________ which ___________, leading to ____________. This ultimately leads to ____________.

A

acetone
acetophenone
benzophenone
absorb UV light beyond 300 nm
triplet excitation with great efficiency
formation of thymine dimers

21
Q

_________ is a furocoumarin which are important in ___________ and _________. Excitation at _________ causes _____________.

A

Psoralen
phototherapy
PDT of skin disease
365nm
effects on denaturation behaviour or intracellular DNA replication

22
Q

4 ways of damaging cellular DNA are __________, __________, __________, and __________.

A

direct ionization of DNA
reaction with e-pre or e-aq
reactions of OH radicals or H2O+
reactions with other radicals such as O2-. , H2O2, H.

23
Q

At 10^-16 s, ____________ occurs. Experimental approaches are __________.

A

excitations and ionization, intratrack reactions
atto-physics, track simulation

24
Q

At 10^-14 s, ____________ occurs. Can use _________ to measure.

A

radical formation from radiolysis of water: .OH, e-pre, e-aq, O2.- , H.
femtochemistry, pulse radiolysis

25
Q

At 10^-12 s, ____________ occurs. Experimental approaches are __________.

A

ultrafast reactions of radicals
femtochemistry; femtobiology

26
Q

At 10^-6 s, ____________ occurs. Experimental approaches are __________.

A

slow reaction of radicals
rapid mix techniques

27
Q

At 10^0 s, ____________ occurs. Experimental approaches are __________.

A

enzymic removal of O2.-, H2O2, enzymic repair of damaged molecules
repair deficient cells

28
Q

At 10^6 s, ____________ occurs. Experimental approaches are __________.

A

cell proliferation
puck plating techniques

29
Q

Direct ionization of DNA damages DNA by _____________ which is most probable in ____________.

A

producing cation radicals
base G through initial ionization of G or from radical transfer to G

30
Q

Double strand breaks can be caused by either _________ or __________.

A

a single energy deposition event
interaction of two SSB formed individually in close proximity

31
Q

The most important lesions produced in chromosomes by radiation is ____________ and may result in ___________.

A

DSBs
cell killing, carcinogenesis, mutation

32
Q

MDS are __________ and are produced by _____________. Consist of __________.

A

multiply damaged sites
cluster of ionizations impinging on DNA
mixtures of lesions

33
Q

DNA-protein cross links affects ________________ but ____________.

A

DNA processing at levels of replication, transcription, repair
role of radiation induced DNA protein crosslinks in radiation response still undefined

PHYS 395 (13 decks)

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