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What are microRNAs?

Posted in MIT, Science Journalism by YPAA on September 29, 2009

MicroRNAs (miRNAs) are tiny molecules composed of ribonucleic acid (RNA) that modulate the expression of genes. In nearly all known cases, these tiny RNAs reduce the level of protein produced by their gene targets.

To accomplish this task, miRNAs chemically pair with messenger RNAs (mRNAs), the molecular intermediates between a gene’s DNA sequence and its protein product. This pairing event essentially sequesters the mRNA, preventing it from being decoded to produce protein.

Recognition of an mRNA by a miRNA is imparted by complementary molecular motifs present in both molecules. These molecular motifs are encoded in the DNA sequence of a genome.

MicroRNAs compose a class of gene regulatory molecules widespread and evolutionarily conserved throughout plants and animals. While miRNAs’ effects on gene expression are modest compared to other modes of gene regulation, en masse their total contribution to gene expression in the cell is significant.

The ~150 word definition of microRNA above I wrote for an assignment in a science journalism class I am taking this semester. (Incidently, you may have noticed the frequency of my contributions to this blog has slowed in recent weeks, resulting from an increased non-blog workload. Sorry.)

The assignment was to write an “explainer” for a key scientific term, like you might see set aside from a longer article (in a Scientific American or Discover type magazine) concerning some scientific idea, that references the term. Thus it is meant for a audience interested in science, but not necessarily familiar with the scientific details of whatever topic is under discussion.

My class had mixed reaction to my explainer. The paragraphs were deemed somewhat disconnected in content from each other, perhaps resembling more of a list of facts in the form of sentences. Some found the voice dry and boring (like that of a scientist’s?).

My goal in writing it was to define microRNAs: (1) What they are; (2) What they do; (3) How they function; (4) Why they are important. I could have started with the importance, but the way I wrote it is the way my brain organizes thoughts. I should learn to think like my reader, and also make the language a little more, um, charming.


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