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From Gene to Protein

From Gene to Protein. How Genes Work. What do genes code for?. How does DNA code for cells & bodies? how are cells and bodies made from the instructions in DNA. DNA. proteins. cells. bodies. The “Central Dogma”. Flow of genetic information in a cell

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From Gene to Protein

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  1. From Gene to Protein How Genes Work

  2. What do genes code for? • How does DNA code for cells & bodies? • how are cells and bodies made from the instructions in DNA DNA proteins cells bodies

  3. The “Central Dogma” • Flow of genetic information in a cell • How do we move information from DNA to proteins? transcription translation RNA DNA protein trait replication

  4. aa aa aa aa aa ribosome aa aa aa aa aa aa From gene to protein nucleus cytoplasm transcription translation DNA mRNA protein trait

  5. Transcription fromDNA languagetoRNA language

  6. RNA Review… • ribose sugar • N-bases • uracil instead of thymine • U : A • C : G • single stranded • Many types of RNA • mRNA, tRNA, rRNA, siRNA… transcription DNA RNA

  7. Transcription • Making mRNA • transcribed DNA strand = template/coding strand • enzyme • RNA polymerase • RNA polymerase is versatile (it slices, it dices!) • Unwinds, unzips, adds in complementary RNA bp’s 3 A G C A T C G T 5 A G A A A C G T T T T C A T C G A C T DNA 3 C T G A A 5 T G G C A U C G U T C unwinding 3 G T A G C A rewinding mRNA template strand RNA polymerase 5 build RNA 53

  8. Initiation: Where to begin? • Promoter region • = binding site before beginning of gene • “TATA box” binding site indicates location • “Upstream” of gene to transcribe/copy • = binding site for RNA polymerase

  9. RNA polymerase Elongation A • Match RNA bases to DNA bases on one of the DNA strands • 5’  3’ direction C U G A G G U C U U G C A C A U A G A C U A 5' 3' G C C A T G G T A C A G C T A G T C A T C G T A C C G T

  10. Termination • Eventually… • RNA transcript is released • RNA polymerase detaches (complete mechanism still not fully known)

  11. intron = noncoding (inbetween) sequence exon = coding (expressed) sequence Eukaryotic genes have junk! • Eukaryotic genes are not continuous • exons = the real gene • expressed / coding DNA • introns = the junk • inbetween sequence intronscome out! eukaryotic DNA

  12. intron = noncoding (inbetween) sequence exon = coding (expressed) sequence mRNA splicing • = “Post-transcriptional processing” • eukaryotic mRNA needs work after transcription • primary transcript = pre-mRNA • mRNA splicing • edit out introns • make mature mRNA transcript ~10,000 bases eukaryotic DNA pre-mRNA primary mRNA transcript ~1,000 bases mature mRNA transcript spliced mRNA

  13. Splicing must be accurate • No room for mistakes! • a single base added or lost throws off the reading frame AUGCGGCTATGGGUCCGAUAAGGGCCAU AUGCGGUCCGAUAAGGGCCAU AUG|CGG|UCC|GAU|AAG|GGC|CAU Met|Arg|Ser|Asp|Lys|Gly|His AUGCGGCTATGGGUCCGAUAAGGGCCAU AUGCGGGUCCGAUAAGGGCCAU AUG|CGG|GUC|CGA|UAA|GGG|CCA|U Met|Arg|Val|Arg|STOP|

  14. snRNPs snRNA intron exon exon 5' 3' spliceosome 5' 3' lariat 5' 3' exon exon mature mRNA excised intron 5' 3' RNA splicing enzymes

  15. Alternative splicing • Alternative mRNAs produced from same gene • when is an intron not an intron… • different segments treated as exons

  16. 3' poly-A tail 3' A A A A A mRNA 50-250 A’s 5' cap P P P 5' G More post-transcriptional processing • Need to protect mRNA on its trip from nucleus to cytoplasm • Enzymes in cytoplasm attack mRNA • protect the ends of the molecule from degrading • add 5 GTP cap • add poly-A tail • longer tail = mRNA lasts longer: produces more protein

  17. aa aa aa aa aa ribosome aa aa aa aa aa aa From gene to protein nucleus cytoplasm transcription translation DNA mRNA protein trait

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