To be topical let's say our cell of
choice is located in the lungs. I will be
comparing the use of RNAi versus CRISPR
and what one I would use to eliminate
the expression of gene A. RNAi stands for
RNA interference this is not a type
of RNA but a mechanism. It is composed of
siRNA, small interfering RNA and miRNA,
micro RNA. These form RISC or RNA
induced silencing complex. siRNA
degrades mRNA or messenger RNA and comes
from mRNA already in the cell,
transposons or viral RNA and targets the
genes that it comes from. miRNA on
the other hand inhibits translation and
it is transcribed from a distinct gene
and targets other genes for regulation. siRNA forms an exact match with the
target site while miRNA does not
as seen in the picture
I'm sure more people have heard of
CRISPR as it is a newer technique which
stands for clustered regularly
interspaced palindromic repeats. CRISPR
is originally a prokaryotic mechanism to
cleave invading DNA for example phage DNA.
CRISPR system detects viral DNA then
makes guide RNA or gRNA that matches to
the viral DNA. A complex is formed with
the Cas-9 protein that cuts the viral
DNA disabling it. While this is a
prokaryotic mechanism researchers have
been able to use it in eukaryotic cells
by being able to change the guide RNA
and have it bind to a specific DNA sequence
that gets cut. This cut DNA sequence in
eukaryotic cell tries to repair itself
but is prone to error which can allow it
to disable the gene. CRISPR can also be
used in many genes at once allowing
researchers to see how genes affect each
other. Another advantage of CRISPR is
that it can insert DNA to the cut site, this
can be helpful if the DNA is originally
damaged to fix it. The two have some
similarities, they both can be used in
eukaryotic cells and both are able to stop /
disable gene expression. Both also use
protein complexes to bind a target site
such siRNA (uses this protein complex) and cut the DNA. While
there are not many similarities they both do
the same job just in different ways. In
my lung cells to stop the expression of
gene A in order to research what it is
that gene A does in the lung cells I
would use CRISPR over RNAi. CRISPR would be
perfect to target specific sequences on
gene A in order to stop the expression
of it, this also allows for more use in
the future by changing the DNA in
certain ways such as inserting a
nucleotide sequence or causing a
frameshift to see how it effects
gene A. Overall I think CRISPR is a
better method and has more applications
