RNA

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RNA

• Transcription Translation get the message out
  and control all of biology in the cell.

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The Central Dogma of Molecular BiologyDNA is
transcribed into RNA which is then translated
into protein
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cytoplasm
transcription
translation
protein
nucleus
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RNA

• RNA molecules are very similar to DNA, except
  that the ribose sugar has an extra -OH group on
  the 2 sugar.
• Instead of tyhmine, RNA uses the base uracil
• Interestingly, single stranded RNA molecules do
  not form a double helix with other RNA strands,
  but only with complementary strands of DNA.
• RNA molecules are much less chemically stable
  than DNA.

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Transcription
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Fig. 2. Structure of an RNA polymerase II
transcribing complex. The bridge helix is shown
in green and the active site metal as a pink
sphere. The DNA helix is colored blue while the
newly synthesized RNA is in red.
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Gene Structure
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Promoter sequence is "upstream" of protein
coding sequence
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mRNA Processing
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Introns are Spliced out of mRNA
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Alternative splicing
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The Central Dogma of Molecular BiologyDNA is
transcribed into RNA which is then translated
into protein
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tRNA carry amino acids to the ribosome
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The Ribosome
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Start Stop Codons

• All proteins start with AUG (codes for
  Methionine)
• Stop codons are UAA, UAG, and UGA

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Reading Frame Mutations
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mRNA signals
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cDNAcDNA is made from RNA by the enzyme
"reverse-transcriptase"
reverse-transcriptase
cDNA
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cDNA can be cloned

• cDNA "copy DNA" or "complementary DNA"
• cDNA can be used in the lab like ordinary DNA
• it can be cloned into plasmids
• and sequenced
• ESTs (Expressed Sequence Tags) are sequences
  from cDNA
• It is fairly easy to make a cDNA "library" which
  contains all of the mRNAs from a batch of cells

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cDNA sequences

• Expressed DNA
• Locates the genes on the chromosome
• Identifies genes that are active in a particular
  group of cells
• Can be quantitative

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Genome Alignment
Remember - why is the alignment between cDNA and
the genome missing sections?
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cDNAs have no INTRONS!

• Can easily predict the protein sequence of the
  gene product (computational translation)
• Cloned cDNAs can be expressed as proteins in
  bacteria