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Exam 2 Radiation Biophysics || Questions and 100% Verified Answers.
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  • Radiation Biophysics
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  • Radiation Biophysics

Mutations in the p53 gene have been found in the majority of human cancers including brain, lung, breast, prostate, thyroid, bladder, colon, liver, musculoskeletal, lymphoma, leukemia, head and neck, and gynecologic cancers. Because of its role in eliminating cells containing damaged DNA, p53 has b...

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  • December 15, 2024
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  • 2024/2025
  • Exam (elaborations)
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  • mutations in the p53 gene have been found in the m

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  • Radiation Biophysics

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Exam 2 Radiation Biophysics || Questions and 100% Verified
Answers.
Mutations in the p53 gene have been found in the majority of human cancers including brain,
lung, breast, prostate, thyroid, bladder, colon, liver, musculoskeletal, lymphoma, leukemia, head
and neck, and gynecologic cancers. Because of its role in eliminating cells containing damaged
DNA, p53 has been described as the? correct answers Guardian of the genome

54. Which of the following proteins localizes to and it used as a marker of DNA double strand
breaks?
A. p43
B. Chk1
C. yH2AX
D. Rb
E. ATM correct answers C. y2AX, the phosphorylated histone variant H2AX, localizes to sites
of DNA dsb rapidly after damage and acts as a docking site for other DNA repair proteins

55. All of the following are phosphatidyl inosital 3-kinase like kinases, EXCEPT:
A. ATM
B. BRCA1
C. ATR
D. RAD3
E. DNA-PK (PRKDC) correct answers B. BRCA1 is not a phosphatidyl inositol 3-kinase like
kinase, whereas ATM, ATR, RAD3, and DNA-PK all fall into this category of protein

56. The transcriptional activity of the tumor suppressor p53 has been shown to be regulated by
all of the following, except:
A. phosphorylation of p53 (TP53) by ATM
B. Changes in the subcellular localization of p53
C. Changes in the ubiquitination of MDM2
D. p19ARF-induced changes in acetylation of p53
E. Binding of FAS ligand (FASLG/CD95-L) to FAS (CD95/APO-1) correct answers E. All of
the processes listed, except binding of FAS ligand to FAS receptor on the plasma membrane,
have been associated with p53 activation. Binding of FAS ligand to FAS receptor activates the
extrinsic pathway to apoptosis, which does not appear to involve p53.

Nucleosome arrays are folded into chromatic fibers which are in turn folded into loop domains.
State as least one of the roles of loop domains. correct answers Important for the organization
and packaging of chromatin in the interphase nucleus and mitotic chromosomes

How do histones and other DNA-bound proteins protect DNA against ionizing radiation? correct
answers histones act as scavengers for radiation-induced radicals

, Mitotic cells are hypersensitive to IR and this correlates with chromatin condensation or
chromatin in the compact form. What is the molecular basis for the hypersensitivity of chromatin
in the compact form? correct answers unknown

57. Sublethal DNA damage is most likely to accumulate:
A. At high doses given at high dose rate
B. At high total doses under hypoxia
C. After high LET radiation
D. After low fractionated doses of radiation correct answers A. Intertrack interactions between
ionization events are more likely at high dose and high dose rate

58. Sublethal DNA damage is most likely to be repaired:
A. After high total doses given at high dose rate
B. If cells are held in a non-proliferative state
C. After high LET radiation
D. Between low fractionated doses of radiation correct answers D. The lower the number of
ionization events in time and space, the more likely they are to be repaird

59. Which of the following radiobiological phenomena occurring between dose fractions has
little or no effect on normal tissue radiation responses?
A. Repair
B. Redistribution of cells in the cell cycle
C. Repopulation
D. Reoxygenation correct answers D. Normal tissues are generally considered to be well
oxygenated

60. Which of the following is true about chromatic structure in the cells?
A. Compacted chromatin is more radiosensitive than non-compacted chromatin
B. During mitosis, cells decompact their chromatic and become radiosensitive
C. Compact chromatin in S phase mediates radioresistancy
D. Compaction facilitates gene transcription correct answers A. Compaction occurs in mitosis
(during which cells are most radiosensitive), which is why chromosomes can be seen under the
microscope during this phase

61. Radiation-induced anaphase bridges generally result from:
A. Dicentric chromosomes
B. Ring chromosomes
C. Acentric fragment
D. Isochromatid breaks
E. A single chromosome break correct answers D. Anaphase bridges generally result from the
induction of isochromatid breaks, which are breaks induced in both chromatids of a sister
chromatid pair following DNA replication in late S phase or G2 of the cell cycle.

62. The minimum whole body radiation dose that can be detected through the measurement of
dicentric chromosomes in peripheral blood lymphocytes is approximately:
A. 0.0005 Gy

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