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By: Jack Liao- HOSTOS- Lincoln Academy of Science
Jingwei Zhang- H.S. for Dual Language and Asian Studies
Gabriell Copeland- Eagle Academy For Young Men
Mentor: Professor Thomas Brennen
Facility: Bronx Community College
Discovery and
Introduction of
RNAi
Potential,
Unsolved
Problems and
Future Research
Function of
RNAi
REFERENCE
What is DNA?
Deoxyribonucleic acid (DNA) is a
nucleic acid —usually in the form
of a double helix— that contains
the genetic instructions specifying
the biological development of all
cellular forms of life, and many
viruses.
DNA never leaves the Nucleus.
RNA
Ribonucleic acid (RNA) is a singlestranded nucleic acid which is
transcribed from the base sequence of
DNA.
dsRNA
Double-stranded RNA (or dsRNA) is
RNA with two complementary strands
which forms the genetic material of
some viruses. It acts as a trigger to
initiate the process of RNA
interference and is present as an
intermediate step in the formation of
siRNAs (small interfering RNAs).
An Unusual Experience with
Unexpected Results
In 1990, scientists in the
US and the Netherlands
experimented with petunia
plants by introducing “Extra”
genes coded for purple
pigmentation to increase the
color purple in the plants.
But instead, a non-pigmented
petunia was created. What
happened?
What is RNAi?
RNA interference (RNAi) is a
mechanism in molecular biology
whereby the presence of certain
fragments of double-stranded
RNA (dsRNA) interferes with
the expression of a particular
gene which shares a homologous
sequence with the dsRNA.
A Double-Stranded
RNA of 200 or more
bases is introduced
into the cell.
RNAi activates.
An RNase III enzyme called
Dicer, chops the doublestranded RNA into small
interfering RNAs (siRNAs)
of 20 or so bases.
The siRNAs then are bound
to the RNA-Induced Silencing
Complexes (RISC) where the
siRNAs are unwound.
Using RNAi, we’re be able to turn
off genes by adding extra copies
or similar genes to the cells.
With this, the potentials are
enormous:
•Cures for Cancer and AIDS may
become available.
•Silencing of non-desired genes.
•Human-Control gene
expressions.
Cancer
Cancer often involves mutant genes that promote uncontrolled cell
growth. In the last few years, researchers have silenced more than a
dozen known cancer-causing genes with RNAi. With RNAi, Cancers
are preventable and curable.
HIV
As soon as RNA interference was discovered in human cells,
scientists began exploring how it could be recruited to battle HIV.
By late 2002, Phillip Sharp and colleagues at MIT announced
they could interrupt various steps in the HIV life cycle with RNAi
molecules.
•At the age of 78, Markey Russell was
diagnosed with Macular Degeneration, a
genetic disease contributing to the
excessive growth of blood vessels which
can burst and destroy her vision.
•In an effort to work with the RNAi
mechanism, Doctors injected dsRNA into
Russell’s eye, signaling grown of blood
vessel, in terms, hoping the homozygous
genes would be destroyed.
•The outcome is promising. Mrs.Russell
can see more clearly now.
Challenges and Future Research
•Finding the function for each of the thousands
of specific genes in the human genome.
•Better understanding of the RNAi
mechanism.
•Utilizing the full potential of RNAi
applications.
•Using RNAi in the treatment and cure of
diseases.
NOVA: ScienceNOW. 2005. 17 July 2006
<http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html>
Ambion: The RNA Company. 2006. 17 July 2006
<http://www.ambion.com/techlib/append/RNAi_mechanism.html>
Wikipedia: The Free Encyclopedia. David D. 2006. 18 July 2006
<http://en.wikipedia.org/wiki/Rnai>
Dr. Sat Bhattacharya
Dr. Thomas Brennan
Harlem Children Society
Bronx Community College (Chemistry Department)
BCC Office of Collaborative Program (College Now)
City University of New York
National Science Foundation
Howard Hughes Medical Institute
Biological Science Curriculum Study
Pathways Bioinformatics & Biomolecular Center