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Gene Expression: From DNA to Protein. Background. Watson & Crick Beedle & Tatum. How Genes are Expressed. Processes: Transcription (DNA to mRNA) Translation (mRNA to protein) Importance of location Eukaryotes Prokaryotes. RNA. Review Types of RNA in Gene Expression

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Presentation Transcript
background
Background
  • Watson & Crick
  • Beedle& Tatum
how genes are expressed
How Genes are Expressed
  • Processes:
    • Transcription (DNA to mRNA)
    • Translation (mRNA to protein)
  • Importance of location
    • Eukaryotes
    • Prokaryotes
slide4
RNA
  • Review
  • Types of RNA in Gene Expression
    • mRNA (messenger)-provides code for protein
    • tRNA (transfer)-carries amino acids
    • rRNA (ribosomal)-directs translation
transcription
Transcription
  • Requires DNA-dependent RNA Polymerase
    • Core enzyme + sigma factor = holoenzyme
  • Three forms in Eukaryotic Nuclei
      • RNA Pol I –Pre-rRNA
      • RNA Pol II**--Pre-mRNA
      • RNA pol III –Pre-tRNA
stage one intiation
Stage One: Intiation
  • RNA recognizes region to be transcribed
    • Promotor regions
      • TATA box
      • CAAT box
stage two elongation
Stage Two: Elongation
  • Complementary mRNA produced from DNA
stage three termination
Stage Three: Termination
  • Often zones with high GC levels
  • Loop and release of mRNA
  • Protection
    • 5’ capped with 7-methyl G
    • 3’ tail polyadenylation
translation
Translation
  • Prokaryotic cells translate immediately into protein
  • Eukaryotic cells process mRNA before translation occurs
    • Cutting out Introns
    • Protecting transcript
processing mrna
Processing mRNA
  • Splicing occurs by sequence
    • snRNA and snRNP (spliceosomes), and/or ribozymes (self-splicing enzymes)
    • Many different proteins can result from one transcript
requirements for translation
Requirements for Translation
  • mRNA
    • Transcript
  • tRNA
    • Carrier for amino acids
  • Ribosomes
    • Two sub-units of protein with three pieces of RNA
nucleotide sequence to protein
Nucleotide Sequence to Protein
  • Codons- 3 nucleotide codes for amino acids
    • 20 amino acides
    • 64 codons
    • 3 stop codons (UGA, UAA, UAG)
    • 1 Start codon (AUG-methionine)
  • Each codon brings in a tRNA anti-codon that contributes one amino acid to the protein
stage one initiation
Stage One: Initiation
  • Small sub-unit of ribosome binds to mRNA
  • Methionine “start”
  • Large sub-unit of ribosome enters
  • Initiation factors involved
stage two elongation1
Stage Two: Elongation
  • Connection
    • Next tRNA enters
    • 1sttRNA “hands” amino acid to 2ndtRNA, then leaves
    • Ribosome slides to free the next space
    • Continuationfor length of protein
    • Elongation factors involved
stage three termination1
Stage Three: Termination
  • Stop Codon is reached
    • RF’s bind to stop codon
    • Protein is released
    • Ribosomal units disassociate
for our next session
For our next session:
  • Exploring factors influencing gene expression
  • Expression and repression of genes
references
References
  • Brooker, R. J. (2011). Concepts of Genetics + Connect Plus Access Card. McGraw-Hill Science Engineering, New York, NY.
  • Brooker, R. J., (2012). Genetics: analysis and principles. 4th Ed. McGraw-Hill Higher Education, New York, NY.
  • King, M. D. (2013). The Medical Biochemistry Page. Retrieved from: http://themedicalbiochemistrypage.org/home.html.
  • McClean, P. E. (2013). Transcription. Retrieved from: http://www.ndsu.edu/pubweb/~mcclean/plsc731/transcript/transcript1.htm
  • Unknown (2013). Three types of RNA polymerase in eukaryotic nuclei. Retrieved from: http://mcb.berkeley.edu/courses/mcb110/ZHOU/lec.5-7.euk_trxn_apparatus.pdf
image sources
Image Sources
  • Cap & Tail http://classconnection.s3.amazonaws.com/681/flashcards/894681/jpg/coding1330783434942.jpg
  • RNA Elongation http://limbiclab.files.wordpress.com/2012/12/limbic_lab_dna_transcription_diagram1.png
  • RNA Initiation http://9e.devbio.com/images/ch05/0503fig1.gif
  • Processing http://www.genomebc.ca/glossary/Alternative%20Splicing%20(colourful)_Image.gif
  • Translation Initiation http://kvhs.nbed.nb.ca/gallant/biology/translation_initiation.jpg
  • Translation Elongation http://kvhs.nbed.nb.ca/gallant/biology/translation_elongation.jpg
  • Translation Termination http://utminers.utep.edu/rwebb/assets/images/17.17_Termination_of_transla.jpg
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