Chapter_17_Biology_Reading - Chapter 17 Biology Reading...

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Chapter 17 Biology Reading -one gene one ezyme hypothesis- that the function of a gene is to dictate teh production of a specific enzyme -however, not all all proteins are enzymes - one gene one polypeptide hypothesis - -However,some genes code for RNA molecules that have important functions in cells though they never translate into protein BASIC PRINCIPLES OF TRANSCRIPTION AND TRANSLATION -synthesis of nucleic acid RNA between DNA and protein synthesis -RNA has ribose instead of deoxyribose -Uracil rather than thymine ***consist of single strand transcription - synthesis of RNA under the direction of DNA messenger RNA - carries a genetic message from the DNA to the protein- synthesizing machinery of the cell translation - actual synthesis of a polypeptide which occurs under teh direction of mRNA - ribosome - site of translation -RNA is used to make proteins because it protects the DNA and allows for multiple copies of the DNA to be made ***In bacteria, a nuclei is lacking- DNA is not segregated from ribosome-->allows translation of an mRNA to begin while its transcription is still in progress -Transcription occurs in the nucleus, translation occurs in the cytoplasm - RNA processing - yielding a finished mRNA from a pre-mRNA -Primary transcript - initial RNA transcript from any gene CODONS triplet code - triplets of nucleotide bases are the smallest units of uniform length that can code for all the amino acids - template strand - one or two DNA strands transcribed for each gene -mRNA is complementary to DNA template -RNA molecule is synthesized in antiparallel direction- 5’-->3’ direction - codons - mRNA base triplets ***codons are also read in the 5’-3’ direction by translation machinery -The three codons that do not designate amino acids are stop codons-->end translation -AUG= codes for methionine and as start signal - reading frame - reading the symbols in the correct groupings TRANSCRIPTION MECHANISM - RNA Polymerase - pries the two strands of DNA apart and hooks together the RNA nucleotides as they base pair along the DNA -can only build in 5’-3’ direction ****doesn’t need a primer, can start a chain
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promoter - the DNA sequence where RNA polymerase attaches and initiates transcription terminator - in prokaryotes, the sequence that end transcription transcription unit - the stretch of DNA that is transcribed into an RNA molecule ****Eukaryotes have three types of RNA polymerase- I, II, III- RNA polymerase II used for mRNA- other two transcribe RNA that are not translated into proteins
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This note was uploaded on 07/14/2009 for the course BILD BILD1 taught by Professor Bever during the Spring '08 term at UCSD.

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Chapter_17_Biology_Reading - Chapter 17 Biology Reading...

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