The STEM Chicksmas Day One: Gene Silencing

For the 12 Days of “The STEM Chicksmas” we’re highlighting 12 scientists who have contributed something innovative and exciting to their field. It is the season of giving, and these brilliant minds have given incredible gifts to the scientific community! This year we’re looking at 12 Nobel Prize winners from the past 15 years in the fields of Physics, Chemistry, and Physiology or Medicine.

Day One: The 2006 Nobel Prize in Physiology or Medicine.

Nobel Prize Medicine 2006, Winners, Findings
Source: Nobel Prize Summary and Nobel Prize Popular Information

All of our genetic information is encoded in our DNA (a double stranded molecule made of nucleic acid pairs)  in localized areas we call genes. Genes contain all of the information that makes us US, from the color of our hair to the types of genetic disorders we might exhibit. When genes have information to encode proteins, it is first copied through a process called transcription onto RNA (a single stranded nucleic acid molecule), which acts as an intermediate for the protein encoding process. The specific type of RNA that passes on this information is called mRNA, or messenger RNA. It defines the amino acid sequence on a protein, which determines its properties. This process of information flow is known as the Central Dogma of Molecular Biology.

In the 1990s, Andrew Fire (Stanford) and Craig Mello (University of Massachusetts Medical School) discovered a surprising attribute of RNA: it can not only encode information, it can also block information in a process called “interference.” Their interest was piqued when scientists tried to make red petunias even redder by injecting a certain gene into the plant, but instead got colorless flowers.

This phenomenon can be explained by the differences in types of RNA. Although mRNA is single-stranded, the scientists discovered a type of RNA that is double-stranded can actually “silence” mRNA. This double stranded RNA is broken up into fragments by a series of protein interactions, and eventually the two strands are also cleaved from each other and bound to a protein complex called RISC. RISC plus these RNA strands can bind to mRNA on its way to protein production. By literally “interfering” with the mRNA’s journey, the genetic information never reaches its destination and the process is interrupted. It is called RNA interference, or RNAi. Fire and Mello measured this in nematodes—they injected “double-stranded RNAi” targeting mRNA coding for proteins related to movement in baby nematodes. The baby nematodes just made odd twitching movements, showing the scientists that the inserted double stranded RNAi “silenced” the gene expression for movement!

The discovery of this mechanism is important not only because it gives better insight into the way information flows in our body, but also because it gives us the ability to control the process. This has potential medical applications (research is being done now to use RNAi to treat degeneration in the eye) as well as has given birth to the field of genetic engineering. After all, if we can make a colorless flower, what else can we do?

To read more, check out the Nobel Prize website here or Fire and Mello’s award winning work here.


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