1 / 23

Transcription Translation

Transcription Translation. Gene expression. - process by which DNA directs protein synthesis two stages :. transcription and translation. Figure 14.UN01. Central Dogma. Protein. RNA. DNA. Gene expression. Differences Between DNA and RNA. Prokaryotes. Figure 14.4a-2.

kevyn
Download Presentation

Transcription Translation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transcription Translation

  2. Gene expression • -process by which DNA directs protein synthesis • two stages: transcription and translation

  3. Figure 14.UN01 Central Dogma Protein RNA DNA Gene expression

  4. Differences Between DNA and RNA

  5. Prokaryotes Figure 14.4a-2 • translation of mRNA can begin before transcription has finished DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide (a) Bacterial cell

  6. Figure 14.4b-3 Eukaryotes Nuclear envelope DNA TRANSCRIPTION • -the nuclear envelope separates transcription from translation; mRNA must be transported out of the nucleus to be translated • Eukaryotic RNA transcripts are modified through RNA processing to yield the finished mRNA Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide Overview: http://www.pbslearningmedia.org/asset/lsps07_int_celltrans/ (b) Eukaryotic cell

  7. Figure 14.5 DNA template strand 3 5 C A C A C A A C G A G T T G T G G T T G C T C A 5 3 TRANSCRIPTION G U U G C U C G U G U A mRNA 3 5 Codon TRANSLATION Protein Gly Ser Trp Phe Amino acid

  8. Figure 14.6 Genetic Code Second mRNA base A U G C UUU UCU UAU UGU U Phe Tyr Cys UUC UCC UAC UGC C U Ser Stop Stop UUA UCA UAA UGA A Leu Stop UUG UCG UAG UGG G Trp CUU CCU CAU CGU U His CUC CCC CAC CGC C 64 codons; 20 amino acids The genetic code is redundant: more than one codon may specify a particular amino acid C Leu Pro Arg CUA CCA CAA CGA A Gln CUG CCG CAG CGG G First mRNA base (5 end of codon) Third mRNA base (3 end of codon) AUU ACU AAU AGU U Ser Asn IIe AUC ACC AAC AGC C A Thr AUA ACA AAA AGA A Lys Arg Met or start AUG ACG AAG AGG G GUU GCU GAU GGU U Asp GUC GCC C GAC GGC G Ala Gly Val GUA GCA GAA GGA A Glu GUG GCG GAG GGG G

  9. Universal Genetic Code Figure 14.7 (b) Pig expressing a jellyfish gene (a) Tobacco plant expressing a firefly gene

  10. Figure 14.10 Transcription Nontemplate strand of DNA RNA nucleotides RNA polymerase RNA polymerase assembles 5’ to 3’ -can start a chain without a primer C C A A T A 5 T 3 U T C 3 end G T U A G C A C U A C C A C A A 5 3 T T T A G G 5 Direction of transcription Template strand of DNA Newly made RNA

  11. Figure 14.8-3 1 2 3 Transcription unit Prokaryotes Promoter 5 3 3 5 Start point RNA polymerase Initiation 5 3 5 3 Template strand of DNA Unwound DNA RNA transcript Elongation Rewound DNA 5 3 3 5 3 5 Direction of transcription (“downstream”) RNA transcript Termination 5 3 5 3 3 5 Completed RNA transcript http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

  12. Figure 14.9 1 2 3 Eukaryotes Promoter Nontemplate strand Transcription factors mediate the binding of RNA polymerase and the initiation of transcription DNA 5 3 T A T A A A A 3 5 A T A T T T T A eukaryotic promoter TATA box Start point Template strand Transcription factors 5 3 Several transcription factors bind to DNA. 3 5 RNA polymerase II Transcription factors Transcription initiation complex forms. 5 3 3 5 3 5 RNA transcript Transcription initiation complex

  13. Figure 14.UN03 Eukaryotic cells modify RNA after transcription DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA Ribosome TRANSLATION Polypeptide

  14. Figure 14.11 RNA Processing 50–250 adenine nucleotides added to the 3 end A modified guanine nucleotide added to the 5 end Polyadenylation signal Protein-coding segment 3 5 AAUAAA AAA AAA G P P P … • Modifications: • The 5 end receives a modified G nucleotide 5 cap • The 3 end gets a poly-A tail • Functions: • Facilitating the export of mRNA to the cytoplasm • Protecting mRNA from hydrolytic enzymes • Helping ribosomes attach to the 5 end Start codon Stop codon Poly-A tail 5 UTR 5 Cap 3 UTR

  15. Figure 14.12 Alternative RNA Splicing Pre-mRNA Intron Intron Poly-A tail 5 Cap 1–30 105– 146 31–104 Introns cut out and exons spliced together mRNA 5 Cap Poly-A tail 1–146 3 UTR 5 UTR Coding segment RNA splicing removes introns (noncoding) and joins exons (translates to amino acids), creating an mRNA molecule with a continuous coding sequence AAUAAA

  16. Figure 14.14 Translation Amino acids Polypeptide tRNA with amino acid attached A cell translates 
an mRNA message 
into protein with the help of 
transfer RNA (tRNA) Ribosome Trp Gly Phe tRNA C C C Anticodon C G A A A A U G G U U U G G C Codons 5 3 mRNA

  17. Figure 14.15 tRNA 3 A Amino acid attachment site C C 5 A Amino acid attachment site G C C G 5 C G G U 3 U A A U A U U C G * G A U C * A A C A C * C U G * Hydrogen bonds U U G G G * G C A G C * * C G A G U * * G A C G Hydrogen bonds C G U A * G A * A C G A A * U 3 5 A G A Anticodon Anticodon Anticodon (b) Three-dimensional structure (c) Symbol used in this book (a) Two-dimensional structure

  18. Figure 14.17 Growing polypeptide Exit tunnel Ribosome Structure tRNA molecules Large subunit E P A Small subunit 5 3 mRNA (a) Computer model of functioning ribosome Growing polypeptide P site (Peptidyl-tRNA binding site) Amino end Exit tunnel Next amino acid to be added to polypeptide chain A site (Aminoacyl- tRNA binding site) E site (Exit site) E tRNA E P A Large subunit mRNA 3 mRNA binding site Small subunit Codons 5 (c) Schematic model with mRNA and tRNA (b) Schematic model showing binding sites

  19. Figure 14.18 P i 1 2 initiation Large ribosomal subunit • 3 stages: • Initiation • Elongation • Termination 3 5 U C A P site Met Met 3 5 A G U Initiator tRNA  GDP GTP E A mRNA 5 5 3 3 Start codon Small ribosomal subunit Translation initiation complex mRNA binding site Small ribosomal subunit binds to mRNA. Large ribosomal subunit completes the initiation complex. http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf http://www.pbslearningmedia.org/asset/lsps07_int_celltrans/

  20. Figure 14.19-3 1 P i 2 P i 3 Elongation Amino end of polypeptide Codon recognition E 3 mRNA Ribosome ready for next aminoacyl tRNA A site P site GTP 5 GDP  E E P A P A Peptide bond formation GDP  Translocation GTP E P A

  21. Figure 14.20-3 P i 2 1 3 Termination Release factor Free polypeptide 5 3 3 3 5 5 GTP 2 Stop codon (UAG, UAA, or UGA) 2 GDP  Release factor promotes hydrolysis. Ribosome reaches a stop codon on mRNA. Ribosomal subunits and other components dissociate.

  22. Figure 14.22 polyribosomes Completed polypeptide Growing polypeptides Incoming ribosomal subunits Polyribosome Start of mRNA (5 end) End of mRNA (3 end) A number of 
ribosomes can 
translate a 
single mRNA 
molecule 
simultaneously (a) Several ribosomes simultaneously translating one mRNA molecule Ribosomes mRNA (b) A large polyribosome in a bacterial cell (TEM) 0.1 m

  23. Figure 14.24 Review DNA TRANSCRIPTION 3 Poly-A RNA polymerase 5 RNA transcript Exon RNA PROCESSING RNA transcript (pre-mRNA) Aminoacyl-tRNA synthetase Intron Poly-A NUCLEUS Amino acid AMINO ACID ACTIVATION tRNA CYTOPLASM mRNA 3 5Cap A Aminoacyl (charged) tRNA Poly-A P E Ribosomal subunits http://www.pbslearningmedia.org/asset/lsps07_int_celltrans/ 5Cap TRANSLATION C C U A A C E A Anticodon A A A U U U U A U G G G Codon Ribosome

More Related