Most genes are present in
the same quantity in every cell - namely, one copy per haploid cell or
two copies per diploid cell.
What genes make an exception to this rule?
a small percentage of the genome is expressed in each cell, and
level at which a gene is expressed can vary widely.
Various techniques can be used
to detect genes and monitor their expression. These techniques use DNA,
or Proteins as the biological material
Gene expression patterns vary
from cell type to cell type (e.g. neurons vs. hepatocytes).
Even within the same cell, gene
expression levels may vary as the cell responds to changes in physiological
In this tutorial we will
describe each method and will discuss its relative pros and cons.