The freshmen view of gene expression is often presented like this,
a relatively simple diagram of a cell showing
the flow of gene expression from the nucleus into the cytoplasm.
We've learned from our basic biology classes,
that gene expression begins with the transcription of DNA to make RNA,
which can then be spliced and polyadenylated,
exported from the nucleus,
and then this genetic information is encoded in the RNA is then translated into protein,
the building blocks of a cell.
And looking as such a simple diagram,
things almost make sense.
But underneath this seemingly simple facade,
this cell really buzzes with biochemical complexity.
Each genome in every cell or plant of animal contains many thousands of genes.
And left to its own accord,
the cell might express every gene in the genome at once.
However, no cell could really function with such a behavior.
Cells have to regulate gene expression,
allowing only the appropriate subset to be expressed in each particular cell type.
Although the genomes of many organisms have been sequenced,
scientists are still struggling with how a cell makes
the decision of which genes to be expressed and which gene to silence.
In one time, many scientists assumed that
the chief regulatory components of the cell were composed of proteins.
However, new data are emerging suggesting that
RNA may play an important regulatory role in
gene expression and a critical role in
the development of cell types creating complex lifeforms.
These new data cause us to study the regions of the genome once considered junk DNA,
the regions of the genome which lie within and around protein encoding genes.
When one adds up the total parts of the genome,
that encode for proteins,
it's clear that the protein encoding portions,
make up only a relatively minor percentage of most complex eukaryotes.
Take for example, in humans it's thought that there's less
than one and a half maybe two percent of the genetic material,
which is translated into protein.
The rest of this information is considered non-coding,
and it is within this dark matter which
scientists are discovering a lot of interesting biology.
To be clear, just because the genome contains a major fraction of non-coding RNA,