Noncoding RNA roles in Gene Expression

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Noncoding RNA roles in Gene Expression
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I. Prior Thinking New Findings

• A. Protein-coding DNA only accounts for 1.5 of
  the human genome.
• B. Most of the rest of the DNA was thought to be
  noncoding and never transcribed. (therefor
  useless DNA)
• C. Recently scientists have found that the genome
  is transcribed into nonprotein-coding RNAs
• 1. In the cell there is a large diversity of RNA
  molecules that play crucial roles in regulating
  gene expression

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II. MicroRNA

• A. MicroRNA (miRNA) are small single stranded
  molecules that are capable of binding to
  complementary sequences in mRNA molecules to
  either degrade an mRNA molecule or block
  translation. (thus regulating gene expression)

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I. Regulation at Stages

• A. All organisms prokaryotes and eukaryotes alike
  have to regulate which genes are expressed.
• 1. both uni- and multicellular organisms must
  continually turn genes on and off in response to
  signals
• B. All cells have the same genome however, the
  genes expressed by each cell is unique allowing
  for cells to carry out specific functions.
• 1. Cells do not differ in genes present but
  differential gene expression

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II. MicroRNA

• B. How do miRNA regulate gene expression
• 1. Made from larger RNA precursors that fold back
  on themselves, forming one or more double
  stranded hairpin structures
• 2. Each hair pin is cut by an enzyme
• 3. One side is degraded the other the miRNA forms
  a complex with proteins
• 4. The complex can bind to a RNA molecule

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III. Small Interfering RNAs

• A. If cells are injected with double stranded RNA
  they turned off expression of genes with the same
  sequences as the RNA. This is called RNA
  interference (RNAi) which is caused by siRNA.
• 1. siRNA are very similar to miRNA