When cells from an AT patient are indicated with a high dose

When cells from an AT patient are indicated with a high dose what can happen? Inhibited cell cycle arrest Slower DNA replication increased sensing of DNA damage illegitimate recombination What is the LD 50 (30) for humans? 4 Gy 0.5 Gy 20 Gy 100 mGy What phase in the growth curves happens after the plateau phase? Lag phase Contact phase Exponential phase None of the above Based on cell survival curves, the most radioresistant cells are: Bone Marrow Cells Mammary Cells Testis Stem cells Human Ataxia Telangiectasia and bone marrow stem cells Which cells are most radiation sensitive? Slow growing cells Cells in cell cycle arrest Rapidly dividing cells Cells from the CNS How many DNA single strand breaks could occur after a 2 Gy dose to a cell? 40 100 2000 500

Solution

17. answer : C

explanation: AT patient irradiated with high dose leads to DNA damage

18. answer: a

19. answer : d

20.answer : d

radioresistant cells : bone , liver, muscle

21. answer : C

radiosensitive directly proportional to rapidly diving cells and inversly proportional to degree of cell proliferation

22. answer : C

explanation : Dose (1-2 Gy) the number of DNA lesion per cell eg: single strand break = 2000

                                                                                                           Double strand break = 40