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ONPS SEM 2 > RBP L2 - DNA Damage by Radiation > Flashcards

RBP L2 - DNA Damage by Radiation Flashcards

1
Q

DNA consists of a backbone of alternating sugar (deoxyribose) and phosphate molecules. One of the four organic bases is attached to each sugar molecule.

A

True

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2
Q

DNA is the principal target for Biological Effect

A

True

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3
Q

The nucleotide in DNA has three parts: a phosphate group, a five-carbon sugar called deoxyribose, and one of four nitrogenous bases – adenine (A), guanine (G), cytosine (C), or thymine (T).

A

True

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4
Q

What holds the two strands of DNA together?

A

Hydrogen bonding between the bases

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5
Q

What is D0?

A

D0 = 37% cell survival

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6
Q

What is D0 for mammalian cells? How much base, SSB and DSBs does this equivilate to?

A

1-2Gy, 1k base and 1k SSB, 40 DSB

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7
Q

Compare SSB and DSB in terms of damage/repair

A

SSB are of little biological consequence. They can be repaired easily using the opposite strand as a template. DSB, if breaks are far then can be repaired individually. If directly opposite, may lead to chromatin snapping

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8
Q

A break in one strand is of little significance because it is repaired readily, using the opposite strand as a template.

A

True

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9
Q

Breaks in both strands, if well separated, are repaired as independent breaks.

A

True

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10
Q

If breaks occur in both strands and are directly opposite or separated by only a few base pairs, this may lead to a double-strand break in which the chromatin snaps in two pieces.

A

True

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11
Q

How much energy does a spur vs. blob contain?

A

Spur has 100eV, Blob has 100-500eV

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12
Q

How many ion pairs dos a spur vs. blob contain?

A

Spur has 3, Blob has 12

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13
Q

How big (diameter) is a spur vs blob?

A

Spur 4nm, Blob 7nm

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14
Q

What is the diameter of DNA? Why is this important?

A

2nm, important because since spurs are 4nm and blob are 7nm, they can break the DNA strand

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15
Q

Are spurs or blobs more common in x-rays?

A

SPURS - 95%

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16
Q

What are some possibilities once DNA is damaged (in terms of repair mechanism)

A

They can just repair normally, so nothing wrong is seen. They may fail to rejoin and deletion happens. OR, broken ends join together and is seen as a mutation

17
Q

The repair mechanisms used for Base repair can be used for DSB repair

A

FALSE!!!

18
Q

What are APE1 and DNA glycosylase?

A

They are ‘removers’ of the base that is wrong “U”

19
Q

What molecule comes and gives the right base for base-excision repair?

A

DNA polymerase

20
Q

What is Nucleotide Excision Repair?

A

It removes bulky adducts in DNA such as pyrimidine dimers

21
Q

What are the two pathways for NER? What is the difference between the two?

A

GG-NER and TC-NER. GG repairs everywhere, TC only repairs at DNA w/ ACTIVELY TRANSCRIBED GENES

22
Q

The mechanism of GG-NER and TC-NER differs only in the detection of the lesion; the remainder of the pathway used to repair the damage is the same for both.

A

True

23
Q

What does Nucleotide Excision Repair consist of (in general terms)

A

Find the damage, cut out the damage along with its surroundings, remove it, repair it, glue it

24
Q

Describe DSB Repair in terms of cell cycle

A

In G1, NHEJ occurs, in S and G2, HRR occurs

Non-homologous End Joining and Homologous Recombination Repair

25
Q

The initial signal for DNA-DNA crosslinks is stalling of the replication fork

A

True

26
Q

What is Mismatch Repair?

A

Removal of small base-base incisions during replication

27
Q

What is the opposite of germ cells?

A

Somatic cells

28
Q

What is the base combination for telomeres?

A

TTAGGG

29
Q

Where is RNA located?

A

In the cytoplasm

30
Q

EAch time normal somatic cell divides, telomeric DNA is lost from the LAGGING strand

A

True

ONPS SEM 2 (12 decks)

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