1 / 20

TRANSCRIPTION

TRANSCRIPTION. DNA. Transcription. mRNA. Ribosome. Translation. Protein. DNA  RNA  Protein. Transcription. DNA is copied into messenger RNA (mRNA) by an enzyme called RNA polymerase in the nucleus mRNA is identical to DNA except Thymine (nucleotide) is replaced by Uracil

soleil
Download Presentation

TRANSCRIPTION

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

  2. DNA Transcription mRNA Ribosome Translation Protein DNA  RNA Protein

  3. Transcription • DNA is copied into messenger RNA (mRNA) by an enzyme called RNA polymerase in the nucleus • mRNA is identical to DNA except Thymine (nucleotide) is replaced by Uracil • mRNA is single stranded

  4. DNA vs. RNA

  5. When a cell needs a specific protein it sends a signal to the nucleus, telling it to make that protein • The nucleus makes a “photocopy” of the piece of DNA that carries the information for the desired protein: mRNA

  6. Transcription

  7. Steps of Transcription • Initiation • transcription machinery (made of RNA polymerases) is arranged on the template strand and binds to the promoter region

  8. a promoter • is a DNA sequence that tells the RNA polymerase • Where to start transcription • Which strand of DNA to transcribe • The direction to take from the start • every gene has a promoter, some are stronger than others

  9. 2. Elongation • RNA polymerase complex unwinds and opens a section of the double helix, about 10 bases at a time • transcription begins at the initiation site • RNA pol. adds bases at the 3’ end, elongating 5’  3’ • many mRNAs are made at once and the synthesis is fast: no proof-reading! • error rate 1/ 10^4

  10. 3. Termination • specific DNA sequences signal the end of transcription • RNA polymerase falls off, mRNA is free to leave

  11. http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.htmlhttp://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html

  12. Post-transcriptional modification • in prokaryotes mRNA can be used directly • often translation begins before the mRNA is completely transcribed! • in eukaryotes mRNA needs to be modified

  13. precursor mRNA mature mRNA • A 5’ guanine cap is added • A 3’ poly-A tail is added • Introns are spliced out - exons code

  14. pre-RNA molecule exon intron exon exon intron intron intron exon exon exon splicesome splicesome exon exon exon Mature RNA molecule RNA Processing

  15. enzymes that splice the pre-mRNA are called spliceosomes • alternative splicing allows for one gene to produce multiple proteins • guanine cap allows easy ribosome recognition • polyA tail allows the ribosome to stay on

  16. start codon A U G G G C U C C A U C G G C G C A U A A mRNA codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 stop codon protein methionine glycine serine isoleucine glycine alanine Primary structure of a protein aa2 aa3 aa4 aa5 aa6 aa1 peptide bonds Messenger RNA (mRNA)

More Related