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Gene Splicing

introns - intervening sequences found in eukaryotic DNA 

  • noncoding DNA that doesn’t show up in mRNA or proteins
  • exons - coding sequences

RNA splicing - cuts apart primary transcript to make final mRNA 

  • occurs in nucleus, before mRNA goes into cytoplasm
  • snRNPs - recognizes intron/exon junctions
  • spliceosome - large complex of snRNPs
    • removes introns by twisting them in lariat shape
  • exon-shuffling - theory that intron-exon arrangements represent shuffling of functional units over time

alternative splicing - splicing primary transcript into many mRNAs 

  • includes different sets of exons
  • experienced by 35-59% of human genes
  • makes 120,000 different mRNAs possible in human cells
  • proteomics - study of proteins

differences between prokaryotic/eukaryotic gene expression 

  • eukaryotic genes have introns, prokaryotic genes don’t
  • prokaryotic mRNA contain transcripts for many genes, eukaryotic mRNA only contain transcript for 1 gene
  • prokaryotes can start translation before transcription is done (no nucleus)
  • 5’ cap and 3’ poly-A tail added to genes by eukaryotes
  • 5’ cap starts translation in eukaryotes, AUG codon starts translation in prokaryotes
  • eukaryotes have larger ribosomes
Subject: 
Biology
Subject X2: 
Biology

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