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BISC 320 > Chiolo Lecture 9 > Flashcards

Chiolo Lecture 9 Flashcards

1
Q

How can DSBs be studied?

A

by imaging repair foci (=’sites’) in cells exposed to ionizing radiation (IR)

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2
Q

What experiments allow to identify proteins required for DSB repair?

A

RNAi experiments

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3
Q

What is the mobility of chromosomes without DSBs?

A

limited mobility

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4
Q

How are DSB repair imaged in live imaging?

A

repair proteins are fused with a fluorescent tag (GFP, YFP, mCherry)

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5
Q

What is the mobility of chromosomes with DSBs?

A

explore more space in the nucleus

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6
Q

What does increased mobility of chromosomes facilitate?

A

homology search

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7
Q

What is pericentromeric heterochromatin mostly composed of?

A
  1. repeated sequences (30% of fly/ human genomes)
  2. mostly composed of DNA repeats = transposons and ‘satellite sequences’
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8
Q

Why are pericentromeric heterochromatin composed of DNA repeats?

A

required for centromere stability

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9
Q

What are repeated sequences used as?

A

repeated sequences on different chromosomes can be used as templates for repair leading to ‘aberrant recombination’

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10
Q

What prevents chromosome rearrangements?

A

specialized mechanisms that regulate repair in repeated sequences, these mechanisms rely on nuclear dynamics

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11
Q

What does aberrant recombination result in?

A

translocations in cancer cells

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12
Q

What forms a distinct ‘domain’

A

Drosophila heterochromatin

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13
Q

What is discovery 1?

A

DSBs leave the heterochromatin domain

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14
Q

What is the discovery 2?

A

HR repair continues at nuclear periphery

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15
Q

Why do heterochromatic DSBs move to the nuclear periphery?

A

to prevent aberrant recombination

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16
Q

What does prevention of aberrant recombination allow?

A

‘strand invasion’ to occur away from other repeated nuclear sequences

17
Q

What is the movement of sister chromatids?

A

move together with the DSB

18
Q

What is discovery 3?

A

nuclear actin filaments drive relocalization

19
Q

What does defective movement result in?

A

defective repair and massive chromosome rearrangements

20
Q

Where does relocalization of DSBs occur?

A

repeated DNA sequences

21
Q

What does relocalization isolate?

A

repair sites from similar sequences on other chromosomes to prevent aberrant recombination

22
Q

What is the function of recombinases?

A

cleaves and rejoin DNA molecules to invert, duplicate, relocalize, and delete portions of the genome

23
Q

How does recombinases cleave and rejoin DNA?

A
  1. serine (or tyrosine) breaks a phosphodiester bond
  2. formation of high energy bond with phosphate
  3. phosphodiester bond with new DNA

BISC 320 (20 decks)

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