bio 36 - BIO 311C Spring 2010 Lecture 36 Wednesday 28 Apr 1...

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BIO 311C Spring 2010 Lecture 36 – Wednesday 28 Apr. 1
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Synthesis of a Polypeptide Chain mRNA polypeptide chain 3’ 5’ direction of ribosome movement along the mRNA ribosome NH 2 * The coded information of only one class of RNA, called messenger RNA (mRNA), is used to specify the sequence of amino acids in polypeptide chains. direction of mRNA movement through the ribosome 3
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From textbook, Fig. 17.24. p. 347 In prokaryotic cells: the primary transcripts of mRNA can be utilized for translation immediately after transcription, and may permit the start of translation well before their transcription is complete. Thus, the mRNA is not processed before it is expressed. * 5’ 3’ 4 Direction of translation d direction of transcription
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Eukaryotic Cell In the nucleus of eukaryotic cells: The primary transcript must first be processed, then must exit through nuclear pores, in order to facilitate translation in the cytoplasmic matrix. Thus, transcription and translation are separated in space and time. From textbook Fig. 17.3, p. 329 * Note: Transcription in eukaryotic organelles (mitochondria and plastids) is very similar to that in prokaryotic cells. It does not require post-transcriptional processing before translation can begin. 5
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primary transcript destined to become an mRNA molecule In the nucleus of eukaryotic cells: Several nucleotide sequences within mRNA primary transcripts mark the transcripts for post-transcriptional processing. Start codon (AUG) that, after processing and movement to the cytoplasm, will signal the translation machinery to start reading the nucleotide sequence and begin making a polypeptide chain. Stop codon (UAG, for example) that will signal the translation machinery to stop inserting amino acids into the growing polypeptide chain. Sequence of nucleotides that indicate this is a mRNA primary transcript that must be processed. 5' * upstream of coding region downstream of coding region coding region 3' 6 Prokaryote cells use the same start and stop codons as do eukaryotic cells.
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a 5" cap and a poly-A tail primary transcript processed transcript Addition of a Modified-G Cap to the 5’ End, and a poly-A Tail to the 3’ End, a pre-mRNA Primary Transcript of a Eukaryotic Cell "UTR" means "untranslated region" of the mRNA molecule. * 5'
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This note was uploaded on 08/29/2010 for the course BIO 49720 taught by Professor Brand during the Spring '10 term at University of Texas.

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bio 36 - BIO 311C Spring 2010 Lecture 36 Wednesday 28 Apr 1...

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