The correct option is
C i - cell growth, ii - differentiation
The normal cells differ from the cancer cells in having the property of cell growth and differentiation in a highly controlled and regulated way. This is because of the contact inhibition property and the presence of checkpoints in cell cycle.
In healthy organisms, natural cell growth gets arrested when two or more cells come in contact with each other. This property of normal/healthy cells is called contact inhibition.
Contact inhibition becomes a powerful anti-cancer mechanism keeping a check on uncontrolled growth of cells. However, in cancerous cells there is a rapid increase in cell count forming a tumor (masses of cells accumulated). This happens because the changes in the genetic material causes the loss of this property of contact inhibition.
Cells keep dividing and follow the cell cycle. The cell cycle is the series of events that take place in a cell that cause it to divide into two daughter cells. The cell cycle consists of four phases like G
1, S, G
2, and M. The S or synthesis phase include DNA replication and the M or mitosis phase include the actual division of cell. The other two phases G
1 and G
2 are called the gap phases.
But some cells do not divide further and undergo maturation into specific cell types (to perform specific functions). This property is called differentiation. They do not proceed beyond the G
1 phase in cell cycle. Such cells are said to be in the quiescent stage or G
0 phase and are metabolically active but will not proliferate or divide.
There are checkpoints in cell cycle, which checks size, nutrients, growth factors, DNA damage etc., in the cell and decides whether or not to move forward with division. These checkpoints include G
1/S checkpoint,G
2/M checpoint and the spindle assembly checkpoint (SAC).
Figure : Checkpoints in cell cycle
In the dedifferentiation process, the cells that have lost the capability to divide and regain their dividing property under certain conditions. For example, dedifferentiation of normal cells leads to the formation of tumor cells.
In the redifferentiation process, the cells divide and produce cells which once again lose their dividing capacity, mature and start to perform specific functions.