Ro_Lecture11

Ro_Lecture11 - DNA base pairs Base pairing Anti parallel...

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1 DNA base pairs Base pairing Anti parallel strands
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2 Base pairing DNA sequence (5’ to 3’) Gene sequence Intergenic sequence
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3 DNA RNA Protein Transcription Translation RNA polymerase Ribosome Nucleus Cytoplasm Process Enzyme Location Eukaryotic Information Transfer: Transcription & Translation ****Beadle and Tatum: Gene = polypeptide****
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4 RNA serves as the intermediary between DNA and proteins Although RNA and DNA are structurally analogous, Three major differences DNA RNA Four bases A T G C Double stranded Deoxyribose sugar backbone Four bases A U G C Single stranded Ribose sugar backbone Most DNA is nuclear Most RNA is cytoplasmic Genes are in the nucleus Proteins are made in cytoplasm
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5 Transcription The synthesis of RNA by the enzyme RNA polymerase using DNA as the template is called transcription For each gene, only one of the two strands of DNA is transcribed mRNA is an exact copy of a gene that is exported to the cytoplasm
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6 Transcription involves THREE distinct processes RNA polymerase catalyzes the synthesis of RNA using the DNA as a template RNA polymerase is a multi-protein complex It consists of four proteins in bacteria (E. coli) 1) Transcription Initiation 2) Transcription Elongation 3) Transcription Termination A GENE is a defined region of DNA It has a start, a body a end.
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7 Initiation of Transcription Initiation involves RNA polymerase recognizing and binding to a specific sequence on the DNA The recognition sequence is called a PROMOTER The sequences are present in the promoters of most E. coli genes These sequences are conserved They are critical for proper functioning of the promoter ---- TTGACAT --------------- TATAAT ---------- ---- AACTGTA --------------- ATATTA ---------- (-10) (15-17) (-35) PROMOTER 5’ 3’ 3’ 5’ antisense sense What do we mean by conserved sequence? Regions of the DNA (gene or non-gene) or protein that share similar nucleotide sequence
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8 Homology is never perfect The sequence homology between genes is not usually perfect Once all the genes are aligned, the most common nucleotide at Each position is used to construct a consensus sequence (15-17 bp) Consensus sequences of promoters ---- TTGACAT --------------- TATAAA ---------- AT ----ATG CCC (-10) (-35) (+1)
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9 Homology (molecular biology) Regions of the DNA (gene or non-gene) that share similar nucleotide sequence Sequence homology is a very important concept Structural homology (nucleotide sequence) implies functional homology Conservation of sequence = Conservation of function Genes with a similar sequence are likely to function in a similar manner (Homologous genes encode for similar proteins, which will have similar functions)
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10 RNA polymerase Bacterial RNA polymerase Core enzyme: four polypeptide subunits: alpha (a), beta (b), beta' (b'), and omega (w) Stoichiometry : 2a:1b:1b’:1w Core RNA polymerase can bind to DNA It catalyzes the synthesis of RNA but it has no specificity.
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This note was uploaded on 04/15/2008 for the course BIO 105 taught by Professor Sullivan during the Fall '08 term at UCSC.

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Ro_Lecture11 - DNA base pairs Base pairing Anti parallel...

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