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RNA - PowerPoint PPT Presentation


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RNA. History. mRNA and tRNA worked out in the 1960s Purification of RNA lead to 23S, 16S, and 4S species and accounted for 85% of all RNA tRNA accounted for about 15% of all RNA Hybridization experiments did not match DNA mRNA accounts for only 1-4% of RNA. Types of RNA. mRNA tRNA

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history
History
  • mRNA and tRNA worked out in the 1960s
  • Purification of RNA lead to 23S, 16S, and 4S species and accounted for 85% of all RNA
  • tRNA accounted for about 15% of all RNA
  • Hybridization experiments did not match DNA
  • mRNA accounts for only 1-4% of RNA
types of rna
Types of RNA
  • mRNA
  • tRNA
  • rRNA
  • snRNA
  • snoRNA
  • siRNA
  • microRNA
primary rna
Primary RNA
  • mRNA (messenger RNA)
    • Transcribed from DNA
    • Is then translated into protein
  • rRNA(ribosomal RNA)
    • Necessary for helping ribosomes make protein (catalysis)
  • tRNA (transfer RNA)
    • Mediates amino acid recognition with codons
other rna
Other RNA
  • snRNA – small nuclear
  • snoRNA – small nucleolar
  • microRNA – micro
  • siRNA – short interfering

These RNA species have a variety of functions and not all of them have been worked out yet.

rna and rfam
RNA and Rfam
  • Pfam is a database we discussed to determine groups of proteins
  • Rfam is a similar database for families of RNA
  • www.rfam.sanger.ac.uk
trna and folding
tRNA and folding
  • tRNA have a unique fold
  • There are multiple websites to determine RNA folding
  • http://rna.tbi.univie.ac.at/cgi-bin/RNAfold.cgi
ribosomal rna
Ribosomal RNA
  • Has a structural and functional role in ribosomes
  • Prokaryotes: 70S which is 30S & 50S, which is 16S, 23S, 5S
  • Eukaryotes: 80S which is 45S which is 18S, 28S, and 5.8S
snrna
snRNA
  • Found in nucleus
  • Involved with splicing and telomer maintenance
  • 5 classes U1, U2, U4, U5, U6
snorna
snoRNA
  • Modify both rRNA and snRNA
  • 2 Classes
    • C/D Box – methylate rRNA
    • H/ACA Box – convert uridine to peudouridine in rRNA
mirna
miRNA
  • Recent discovery
  • Small approximately 22 nucleotides
  • Function to down regulate protein expression.
  • http://www.mirbase.org/search.shtml
rnai sirna
RNAi (siRNA)
  • Double stranded RNA
  • Small, artificial
  • Degradation by RISC and Dicer
  • Protective mechanism for plants and animals
slide13
mRNA
  • Coding RNA
  • Central Dogma “one gene – one protein”
    • No longer valid
    • Alternative splicing, regulation, introns, etc.
  • Altered expression by:
    • Region, development, environment, disease, gene activity
slide14
mRNA
  • Key research areas
    • mRNA expression database
      • There is a DNA database, but is an mRNA database equally good?
      • Potential problems with and mRNA database
      • How to measure mRNA expression
mrna expression
mRNA expression
  • Steady-state mRNA (polyA isolation)
    • Transcriptional control
    • RNA processing control
    • RNA export control
    • RNA surveillance control
est database
est database
  • How to study mRNA
    • Highly unstable, need to make cDNA
      • Turn mRNA into DNA with reverse transcriptase
      • Clone into a vector
      • Sequnce (this is called an express sequence tag EST)
    • ESTs can be isolated from specific cells at specific times under specific conditions.
    • This can aid in finding when types of proteins MAY be expressed