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Gene Technology

Fundamental Features of Eukaryotic Genes. Fundamental Features of Eukaryotic Genes. Gene Technology. Processing. Lecture 4 – Chapter 5. Fundamental Features of Eukaryotic Genes. Processing of eukaryotic mRNA: -> Modification of 5’ end (Cap) -> Modification of 3’ end (poly A)

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Gene Technology

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  1. Fundamental Features of Eukaryotic Genes Fundamental Features of Eukaryotic Genes Gene Technology Processing Lecture 4 – Chapter 5

  2. Fundamental Features of Eukaryotic Genes Processing of eukaryotic mRNA: -> Modification of 5’ end (Cap) -> Modification of 3’ end (poly A) -> Splicing (removal of introns) -> editing Gene Technology

  3. Fundamental Features of Eukaryotic Genes The Intron/Exon concept Gene Technology

  4. Fundamental Features of Eukaryotic Genes The Intron/Exon concept Gene Technology Organization of the β-globin (human β subunit of hemoglobin) gene

  5. Fundamental Features of Eukaryotic Genes Splicing -> cutting out of introns Gene Technology 20-50 bp Splicing enhancers – silencers -> regulate alternative splicing Human: ~25.000 genes coding for ~100.000 proteins !!!

  6. Fundamental Features of Eukaryotic Genes Splicing -> cutting out of introns Gene Technology

  7. Fundamental Features of Eukaryotic Genes Splicing is done by a RNA and protein complex -> spliceosome Gene Technology

  8. Fundamental Features of Eukaryotic Genes Gene Technology

  9. 5’ Cap site: -> 7-methylguanosine Gene Technology

  10. Fundamental Features of Eukaryotic Genes Poly(A) tail -> only added to mRNA transcribed by RNA polymerase II Gene Technology

  11. mRNA Processing Gene Technology

  12. mRNA Processing Gene Technology Splicing factors -> recognize splice sites Polyadenylation factors -> recognize poly(A) sites

  13. Fundamental Features of Eukaryotic Genes Alternative Splicing -> different proteins Gene Technology

  14. Fundamental Features of Eukaryotic Genes Alternative Splicing -> different proteins Gene Technology

  15. Fundamental Features of Eukaryotic Genes Alternative Splicing + Alternative Polyadenylation-> different proteins Gene Technology

  16. Fundamental Features of Eukaryotic Genes Alternative Splicing + Alternative Polyadenylation-> different proteins Gene Technology Cell type specific adenylation !!!

  17. Alternative Splicing +Alternative Polyadenylation-> different proteins Gene Technology Cell type specific modification of the mRNA of the α-tropomyosin gene

  18. Alternative Splicing +Alternative Polyadenylation-> different proteins Process of sex determination in Drosophila: -> splicing event directs development of embryo Gene Technology

  19. Fundamental Features of Eukaryotic Genes Errors in splicing -> cause disease Gene Technology Disruption of splice site in β-globin gene -> β-Thalassemia

  20. Fundamental Features of Eukaryotic Genes Introns have been aquired and lost during evolution Gene Technology • Archaea -> have introns (self-splicing) • Bacteria -> have no introns (except: Cyanobacteria -> involved in development of plants) • Eukaryotes -> have introns • -> during evolution introns are aquired or lost -> gene families !!! • -> insulin or tubulin

  21. Fundamental Features of Eukaryotic Genes Introns have been aquired and lost during evolution Gene Technology

  22. Fundamental Features of Eukaryotic Genes Exons often define protein domains -> exon shuffling -> protein evolution Introns -> facilitate genetic variation By recombination of exons (domains) -> exon shuffling -> New protein have been designed by nature by putting protein domain blocks together Gene Technology Low density lipoprotein receptor Result from known proteins -> all proteins are made up of only 1000-7000 exons !!!

  23. Fundamental Features of Eukaryotic Genes Introns can have function Gene Technology Tumor repressor genes : different promoter, but share 2 exons -> Genes can also be found within introns of other genes

  24. Fundamental Features of Eukaryotic Genes Protein families arise from gene duplication Duplication allows one copy to undergo mutations without selection pressure -> accumulations without selection -> genetic drift Genetic drift leads to new function of protein (enzyme acting on different substrate) -> genetic diversity Gene Technology β-globins: -> Evolved from same gene -> different subunits have different physiological properties -> expressed at different times during development

  25. Fundamental Features of Eukaryotic Genes Protein families arise from gene duplication Unequal cross-over between similar sequences (nonhomologous) -> chromosome with duplication Mutations can be corrected by gene conversion -> break of DNA of normal allele -> base pairing of mutant allele with normal allele -> way of eliminating deleterious mutations Gene Technology

  26. Fundamental Features of Eukaryotic Genes Protein families arise from gene duplication Gene duplication can also lead to pseudogenes -> nonfunctional genes Gene Technology

  27. Fundamental Features of Eukaryotic Genes RNA Editing -> posttranscriptional Addition or substraction of nucleotides -> correct reading frame Gene Technology

  28. Fundamental Features of Eukaryotic Genes RNA Editing Guide RNA (gRNA) acts as template to add nucleotides to pre-mRNA -> not coded by DNA Gene Technology

  29. Fundamental Features of Eukaryotic Genes RNA Editing Gene Technology Apolipoprotein B: Plasma lipoprotein RNA editing -> introduction of STOP codon -> cell type specific protein

  30. Fundamental Features of Eukaryotic Genes Different levels of gene expression control Gene Technology

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