The genetic coding or expression that determines our dna and messaging for cells is

The correct answer is "available in all cells but is idle in some cells and active in others".

All cells in the human body have genetic information stored in the nucleus in the form of chromatin. In cells that are not actively dividing such as in neurons, skeletal muscle cells, etc., the genetic information is idle and formed as heterochromatin. In cells that are actively dividing such as in epithelium of the digestive tract, the genetic information is active and formed as euchromatin. 

Ithink its because more have died recently than in the past.