RNA Processing

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RNA Processing

• Chemical Modifications of Transcripts

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Information Flow From DNA
replication
DNA
transcription
processing
RNA
translation
Protein
3
Types of RNA Produced by Transcription

• Messenger RNA
• Contains the code words for the sequence of
  amino acids in a specific protein
• CODON group of three nucleotidesacting as a
  code word for an amino acid

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Arrangement of Codons on mRNA
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Types of RNA Produced by Transcription

• Transfer RNA
• Translates the message by bringing a specific
  amino acid into the correct position on the
  growing protein chain
• Has ANTICODON a group of three nucleotides on a
  tRNA that recognizes a mRNA codon
• Has amino acid attachment site

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Types of RNA Produced by Transcription

• Ribosomal RNA
• One of the structural components of the
  ribosome
• Ribosome organelle where protein
  synthesis occurs
• Has sites to bind both mRNA and tRNA

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Interrupted Genes
Eukaryotic Genes have interruptions within
regions coding for protein intron
interrupting sequence exon portion of coding
region
Processing of the pre-mRNA is required to remove
introns and join exons.
Translated to Produce Protein
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mRNA Processing
DNA
Untranslated Region (UTR)
UTR
Add 5 cap
Cleave at 3 endAdd 3 poly-A tail
Remove Introns Splice Exons together
Stop Codon
Start Codon
Mature mRNA leaves for cytoplasm
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Applying Your Knowledge

• Which of the following molecules lacks introns?
  
• Pre-mRNA
• DNA
• Mature messenger RNA
• All of these lack introns
• None of these lack introns

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Intron Removal for Ovalbumin mRNA
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Addition of a 5-Methyl Guanine Cap
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Cleavage and Polyadenylation of 3 end

• Pre-mRNA is cleaved 11-30 nucleotides downstream
  of the AAUAAA consensus sequence.
• 50-200 Adenine nucleotides are added
  enzymatically to the resulting 3 end.

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Identifying Sites for Intron Removal
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Steps in Splicing
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Alternative Splicing
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Multiple 3 Cleavage Sites
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RNA Editing
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Applying Your Knowledge

• A poly-A tail (repeating sequence of adenine
  nucleotides) is added to _____ of the primary
  transcript.
• The 3 end
• The 5 end
• Either the 3 end or the 5 end
• Both the 3 end and the 5 end
• Neither the 3 end nor the 5 end

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Applying Your Knowledge

• Which molecule contains the information for
  assembling the amino acids in the correct order
  in the protein?
• rRNA
• tRNA
• mRNA
• All of these
• None of these

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tRNA Processing
Nucleotide Addition
Cleavage
Splicing
NucleotideModification
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rRNA Processing