HC6- DSB repair visualization

Question 1

size DNA double helix

Answer 1

2 nm

Question 2

nucleosome core

Answer 2

8 histon molecules > tetramer of 2 H3 and 2 H4 with 2 H2A/H2B dimers

Question 3

Histone H1

Answer 3

linker molecule

Question 4

size nucleosome core

Answer 4

11 nm

Question 5

size beads on a string

Answer 5

30 nm > 300 nm

Question 6

fiber width

Answer 6

250 nm

Question 7

chromosome size

Answer 7

1400 nm

Question 8

DSBs caused by

Answer 8

• ionizing radiation
• UV light
• metabolic processes

Question 9

foci are formed by

Answer 9

most proteins involved in DNA repair

Question 10

DNA repair proteins upon radiation

Answer 10

relocate to sites of DNA damage

Question 11

DNA repair proteins

Answer 11

RNF168, 53BP1, MDC1

Question 12

GFP

Answer 12

for visualization and quantification of DNA repair proteins

Question 13

diffusion of DNA repair proteins

Answer 13

get to DSBs by chance

Question 14

laser microirradiation (quantifying accumulations)

Answer 14

readout for repair activities

Question 15

drawbacks laser microirradiation

Answer 15

• dosage difficult to establish and control
• mostly UV-type DNA lesions
• large dosage concentrated in small area of the nucleus

Question 16

ultra-soft X-ray irradiation microscope adavantages

Answer 16

• precise dosage control
• clinically relavent radiation
• spatial control of radiation through slits
• realtime imaging

Question 17

53BP1

Answer 17

decides which pathway of repair will happen

Question 18

RNF8 and RNF168 (bad timing)

Answer 18

asynchronous and uneven accumulation

Question 19

duration of accumulation at individual DSBs

Answer 19

variable

Question 20

histone acetylation status

Answer 20

affects chromatin organization

Question 21

addition of acetyl groups leads to

Answer 21

histone relaxation by histone acetyl transferases (HATs)

Question 22

removal of acetyl groups leads to

Answer 22

histon condensation by histone deacetylases (HDACs)

Question 23

histone acetylation affects accumulation initiation RNF168

Answer 23

complexity chromatin impacts accumulation kinetics

Question 24

alpha particle irradiation

Answer 24

• accelerated helium ions > induces complex DNA lesions
• linear tract of DSBs

Question 25

complexity of DSBs affects

Answer 25

speed of detection

Question 26

free radical involvement DSBs

Answer 26

by oxygen radicals formed through water radiolysis

Question 27

oxygen radicals

Answer 27

short-lived, extremely reactive

Question 28

DMSO

Answer 28

free-radical scavanger