Biology Chapter 17

Biology Chapter 17 - Chapter 17 From Gene to Protein Basic...

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Chapter 17: From Gene to Protein Basic Principle of Transcription - Genes provide the instructions for making specific proteins - Getting from DNA to protein requires two major stages o Transcription: The synthesis of RNA under the direction of DNA (General term for the synthesis of any kind of RNA on a DNA template) DNA strands provides a template for the synthesis of a new complementary strand during DNA replication, it provides a template for assembling a sequence of RNA nucleotides Resulting RNA molecule is a faithful transcript of the gene’s protein building instructions Messenger RNA (mRNA) carries a genetic message from the DNA to protein synthesizing machinery of the cell o Translation: The actual synthesis of a polypeptide, occurs under the direction of mRNA The cell must translate the base sequence of an mRNA molecule into the amino acid sequence of a polypeptide Sire of translations is in the ribosomes - Nuclear envelop separates transcription from translation in space and time - Transcription occurs in the nucleus o mRNA is transported to the cytoplasm, where translation occurs - Pre-mRNA (Primary Transcript): Transcription of a protein coding eukaryotic gene, an initial RNA transcript - RNA Processing: Yields the finished mRNA Condons: Triplet of Bases - Triplets of nucleotide bases are the smallest units of uniform length that can code for all the amino acids - Triplet Code: The genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, three nucleotide words - During transcript the gene determines the sequence of bases along the length of an mRNA molecule - Template Strand: The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript - An mRNA molecule is complementary rather than identical to its DNA template because RNA bases are assembled ion the template according to base pairing rules - Condons: mRNA base triplets o Written in the 5’-3’ direction o Complementary to the template strand and thus identical in sequence to the mRNA except that they have a T instead of a U (T pairs with the A) - During translation the sequence of codons along the mRNA molecule is decoded or translated into a sequence of amino acids making up a polypeptide chain Cracking the Code - The three condons that do not designate amino acids are “stop” signals, or termination condons, marking the end of translation o Ex) UAA, UGA, UAG - Condon AUG has a dual function: it codes for the amino acid methionine (Met) and functions as a “start”
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This note was uploaded on 11/04/2010 for the course BIO 107 taught by Professor Abott during the Fall '09 term at UConn.

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Biology Chapter 17 - Chapter 17 From Gene to Protein Basic...

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