Lecture 8 - 8 Information Transfer II – Gene...

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Unformatted text preview: 8. Information Transfer II – Gene Structure & Expression – Part I. Iain McKinnell – Dept Biology The Connection between DNA, RNA, and Protein What is DNA actually passing on?….DNA encodes information required to build and maintain an organism's cells : genes . Understanding of DNA structure (in particular, complementary base pairing) determined mechanism of gene expression… Genes specify either protein or RNA products Do Genes Encode Proteins? Proteins are assembled from amino acids – how do we know that genes specify the amino acid sequence of proteins? 1940s: Beadle & Tatum studied Neurospora crassa (orange bread mould). Used X-rays to produce nutritional mutants ( auxotrophs ) Each mutant had defective gene for enzyme needed to synthesize a particular nutrient How Do Genes Specify Enzymes? How Do Genes Specify Enzymes? Fig. 14-2, p. 298 Gene – enzyme relationship. Do Genes Encode Proteins? One gene – one enzyme hypothesis Direct relationship between genes and enzymes One gene – one polypeptide hypothesis Not all proteins are enzymes Functional proteins sometimes contain one or more subunits ( polypeptides ) Different genes encode each distinct subunit Genes to Proteins Transcription Nucleotide sequence in DNA is copied into a complementary sequence in an RNA molecule Template strand of DNA is used to create messenger RNA ( mRNA ) Translation Sequence of nucleotides in mRNA molecule specifies amino acid sequence in polypeptide Ribosome assembles the amino acid sequence Genetic Code...
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This note was uploaded on 10/20/2011 for the course BIOL 1103 taught by Professor Mckinnel during the Fall '11 term at Carleton CA.

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Lecture 8 - 8 Information Transfer II – Gene...

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