1 / 40

PROTEIN SYNTHESIS

PROTEIN SYNTHESIS. GENES & PROTEINS. Garrod : “inborn errors of metabolism” Linked genes & phenotypes Alkaptonuria – black urine, inherited, inability to break down alkapton Beadle & Tatum : “one gene – one enzyme” Experimented with Neurospora crassa

priscilla-roman
Download Presentation

PROTEIN SYNTHESIS

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. PROTEIN SYNTHESIS

  2. GENES & PROTEINS Garrod: “inborn errors of metabolism” • Linked genes & phenotypes • Alkaptonuria – black urine, inherited, inability to break down alkapton Beadle & Tatum: “one gene – one enzyme” • Experimented with Neurospora crassa • 3 classes, all unable to synthesize arginine (a.a.) Revision: “one gene – one polypeptide” • not all gene products are enzymes

  3. Each mutant unable to synthesize one of the necessary enzymes for one step in the arginine pathway

  4. GENE TO PROTEIN: OVERVIEW mRNA TRANSCRIPTION CODON TRIPLET CODE PRIMARY TRANSCRIPT TRANSLATION RNA PROCESSING TEMPLATE STRAND

  5. TERMINOLOGY Transcription: DNA → RNA Translation: mRNA → protein mRNA: carries genetic “code” from DNA to ribosome RNA processing: yields finished mRNA Primary transcript: initial RNA transcript Triplet code: genetic instructions as a series of 3 nucleotides Template strand: DNA strand that is transcribed Codons: mRNA base triplets

  6. PROKARYOTIC CELL • No processing • No nuclear membrane • Transcription & translation • occur simultaneously Eukaryotic cell

  7. CRACKING THE GENETIC CODE • Nirenberg – 1st codon, UUU for phenylalanine • Redundancy but no ambiguity • Reading frame – group of 3 nucleotides, must be read in order • mRNA nucleotides read from left to right (5’-3’) in groups of 3 • Message written w/o spaces but read as a series of non-overlapping 3 letter words (codons). • Summary: Genetic information is encoded as a sequence of • non-overlapping base triplets or codons, each of which is translated into a specific amino acid

  8. STAGES OF TRANSCRIPTION INITIATION ELONGATION TERMINATION

  9. INITIATION • RNA polymerase binds • to promoter • DNA strands unwind • Polymerase initiates RNA • synthesis at the start • point

  10. ELONGATION • Polymerase moves downstream, unwinding the DNA & elongating the RNA transcript 5’→3’ • DNA strands reform double helix

  11. TERMINATION • Polymerase transcribes terminator sequence which signals end of transcription unit • RNA transcript released and polymerase detaches

  12. Transcription factors – mediate the binding of RNA polymerase and the initiation of transcription Transcription initiation complex – assembly of transcription factors and RNA polymerase TATA box – crucial promoter DNA sequence for forming the Initiation complex

  13. PROCESSING • List 4 components of mRNA processing • Explain how tRNA is activated

  14. RNA PROCESSING mG cap Poly A tail

  15. RNA PROCESSING Introns removed Exons spliced

  16. 1) Pre-mRNA combines with small nuclear ribonucleoproteins (snRNPs) and other proteins → spliceosome 2) Within spliceosome, snRNA base-pairs with nucleotides at ends of intron 3) RNA transcript cut to release intron and the exons are spliced

  17. TERMINOLOGY • Ribozymes – RNA molecules that function as enzymes • Alternative RNA splicing – one gene, multiple products depending on which segments are treated as exons • Domains – independently folding part of a protein, discrete structural & functional regions; one domain active site, another attachment site

  18. tRNA • Small 75-85 nucleotides • Anticodon • Amino acid attachment • site (CCA) • Processed in cytoplasm • Transcribed in nucleus

More Related