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Gene Expression From gene to protein

Gene Expression From gene to protein. Transcription and Translation. Prokaryotes – mRNA translated immediately Eukaryotes – pre-mRNA processed before leaving the nucleus as mRNA. Transcription. STEP 1 – Initiation Occurs at a promoter. STEP 2 – Elongation mRNA transcript lengthens.

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Gene Expression From gene to protein

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  1. Gene ExpressionFrom gene to protein Transcription and Translation

  2. Prokaryotes – mRNA translated immediately • Eukaryotes – pre-mRNA processed before leaving the nucleus as mRNA

  3. Transcription

  4. STEP 1 – InitiationOccurs at a promoter

  5. STEP 2 – ElongationmRNA transcript lengthens

  6. STEP 3 – TerminationmRNA transcript released

  7. RNA processingalteration of pre-mRNA

  8. RNA processingRNA splicing • Introns – intervening sequences – noncoding segments on pre-mRNA • May regulate gene activity • Enable genes to give rise to two or more different polypeptides • Facilitate evolution through exon shuffling • Exons – expressed sequences on pre-mRNA • Signal for splicing is a short sequence at the ends of introns

  9. small nuclear ribonucleoproteins (snRNPs) with snRNA recognize splice sites • snRNPs + proteins  spliceosome • release introns • join together exons that flank introns

  10. Translation Overview • mRNAmoves through ribosome • codonsare translated into amino acids • tRNAmolecules: anticodonand amino acid ends • amino acidsadded to a growing polypeptide chain • rRNA molecules + proteins  ribosomes

  11. tRNA structure

  12. Ribosome structure

  13. Building a polypeptide

  14. Step 1 - Initiation

  15. Step 2Elongation

  16. Step 3 – Termination

  17. Given the following sequence on a template DNA strand 3’ TAT AAA CCG TAC GGA TAG ACA CCG AAA ATC CGG GCA 5’ • What is the sequence on the non-template strand? 5’ ATA TTT GGC ATG CCT ATC TGT GGC TTT TAG GCC CGT 3’ • What is the mRNA sequence transcribed? 5’ AUA UUU GGC AUG CCU AUC UGU GGC UUU UAG GCC CGU 3’ • What is the STOP codon? UAG • What is the anticodon attached to the tRNA that corresponds to the STOP codon? There is no tRNA that corresponds to the STOP codon. Release factors take their place. • What is the amino acid sequence in the polypeptide product? Met – Pro – Ile – Cys – Gly - Phe

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