Chapter 15 Noncoding RNAs

You Must Know The role of noncoding RNAs in control of cellular functions.

Only a small fraction of DNA encodes proteins, and a very small fraction of the non-protein-coding DNA consists of genes for RNA such as rRNA and tRNA. A significant amount of the genome may be transcribed into noncoding RNAs (ncRNAs). Noncoding RNAs regulate gene expression at several points.

Chromatin modification Transcription RNA processing Translation mRNA degradation Protein processing and degradation

Micro RNA (miRNA) miRNA- protein complex The miRNA binds to a target mRNA. 1 mRNA degraded Translation blockedmRNA degraded If bases are completely complementary, mRNA is degraded. If match is less than complete, translation is blocked. 2

miRNA Translation blockedmRNA degraded The miRNA binds to a target mRNA. If the mRNA being degraded coded for a protein that promotes cell division in multicellular organism, what would happen if a mutation disabled the gene encoding the miRNA that triggers this degradation?

(February 7, 2015) According to a new study by Cancer Research UK, the number of people with cancer risks has risen steeply over the years. If an average person’s chances to get cancer in his/her lifetime were just over 30% a few years ago, now it is over 50%. According to researchers, some of the factors behind this rise in number are increased life span, unhealthy diet, and other lifestyle changes.

Another class of small RNAs are called small interfering RNAs (siRNAs). siRNAs and miRNAs are similar but form from different RNA precursors. The phenomenon of inhibition of gene expression by siRNAs is called RNA interference (RNAi).