Question

If you study outside on a sunny day, some of your epidermal cells may have received too much UV radiation, causing DNA damage.

1. Which cell cycle checkpoint proteins may have been induced in response to this stress, to halt the cell cycle?

2. If the DNA damage cannot be repaired, what might be the final out come?

Answer 1

1. The UV radiation is ionizing high energy radiation that causes extensive DNA damage (Ec: Thymine dimers). The presence of these lesions does not allow the progress of the cell cycle due to the G2-M checkpoint. The G2-M checkpoint monitors the status of the genome in the cell and triggers the entry into the M-phase. If DNA damage is identified, the cell cycle would stall.

2. If the DNA damage is small and can be repaired, the cell can re-enter the cell cycle after the completion of the repair process. However, if the damaged DNA is large and cannot be repaired, the cell enters the apoptosis pathway.
Apoptosis = Programmed cell death
i.e. the cell would be killed to protect other cells from the damage.