Place the following events in one of the arrest pathways in the correct order st
ID: 222274 • Letter: P
Question
Place the following events in one of the arrest pathways in the correct order starting with a G_2 cell detecting the presence of DNA damage caused by UV irradiation. The cell is arrested in G_2. The Cdc25 molecule becomes a target for a special adaptor protein that binds to the Cdc25 phosphatase in the cell cytoplasm. Cdk1 in the nucleus remains in an inactive state since its inhibitory phosphate groups cannot be removed by Cdc25. Chk1 phosphorylates Cdc25 on a particular serine residue. Cdc25's phosphatase activity is inhibited and its importation into nucleus is prevented. ATR kinase is activated and phosphorylates a checkpoint kinase, called Chk1. ATR kinases are recruited to sites of protein-coated, single-stranded DNA, like those created as UV-damaged DNA is repaired. 2 - 4 - 5 - 3 - 1 - 6 - 7 7 - 6 - 4 - 5 - 2 - 3 - 1 7 - 6 - 4 - 2 - 1 - 5 - 3 7 - 6 - 4 - 2 - 5 - 3 - 1Explanation / Answer
Answer: (D) 7-6-4-2-5-3-1
Explanation: Cell cycle checkpoints are essential for controlling the cell cycle and ensuring that enough signals and nutrients are present for cell division and the DNA is properly duplicated. One such checkpoint is G2 checkpoint, where the cell cycle is arrested, due to unequal DNA replication or DNA damage.
When DNA is damaged following UV rays irradiation, a series of intracellular signaling takes place and the cell cycle is arrested at G2 phase. The series is as follows:
7) ATR kinase are recruited to sites of protein-coated, single-stranded DNA.
6) ATR kinase is activated and phosphorylates a checkpoint kinase, called Chk1.
4) Chk1 phosphorylates Cdc25 on a particular serine residue.
2) The Cdc25 molecule becomes a target for a special adaptor protein that binds to the Cdc25 phosphatase in the cell cytoplasm
5) Cdc25's phosphatase activity is inhibited and its reimportation into the nucleus is prevented.
3) Cdk1 in the nucleus remains in an inactive state since its inhibitory phosphate groups cannot be removed.
1) The cell is arrested in G2.