<span>The metabolic activity of a specific region of the living rat brain can be revealed by measurement of Fos protein concentration.
c-Fos is a proto-oncogene that is the homolog of the retroviral oncogene v-fos. It was first discovered in rat fibroblasts as the transforming gene of the FBJ MSV.</span>
<span>They are not visible because the chromatin coils up,shortens,and thickens.</span>
They don't reproduce, as far as I know. They are produced in bone marrow.
The purpose of spindle fiber is to divide the chromosomes in a parental cell to make them into two daughter cells.
