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Download Lecture Chpt. 17 II Transcript
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Central Dogma DNA Transcription RNA Translation Polypeptide WHAT, in the world is a DOGMA??????? Central Belief DNA Transcription RNA Translation Polypeptide Central Dogma DNA= genotype Transcription RNA= the messenger Translation initiatio n Transcription unitarea of DNA to be transcribed (turned into a protein). 5” --> 3’ direction from daughter RNA polymerase enzyme that unzips DNA & adds mRNA to the DNA @ promoter point… transcription begins here~no primer needed!! initiatio Promotorarea of DNA in which RNA polymerase can bind upstream from transcription unit About 100 nucleotides long. Holds TATA box gene 1)Transcription factors proteins that bind to DNA before RNA polymerase at the TATA box gene proteins that help bind the polymerase 2) RNA polymerase (enzyme) can now attach to strand and double helix unwinds... untwists 3)Elongation of mRNA strand 4)mRNA peels away from polymerase 5)DNA re-forms NOTE: U not T elongatio Elongation • Enzyme moves 5’------> 3’ on RNA strand • Rate is about 60 nucleotides per second. 6) Terminator sequencewhen polymerase hits this particular sequence, transcription ends termination IN EUKARYOTES Pre-RNA is the result 5’ 3’ IN EUKARYOTES Pre-RNA 5’ 1) 5’ Cap -protection against digestive enzymes degrading the RNA. - “attach here” symbol (later) for attachment to ribosome. 3’ IN EUKARYOTES Pre-RNA 5’ 3’ 2) 3’ Cap -protection against digestive enzymes from degrading RNA. - helps “ship” RNA from nucleus to ribosome. RNA splicing pre-mRNA + snRNA’s (small nuclear RNA) recognize splice -sites on pre-mRNA + proteins spliceosome connects splice sites on pre-mRNA Intron = cut out of RNA stays IN the nucleus Exon = stays on & spliced together. EXPRESSED Introns - Function • Left-over DNA (?) • Way to lengthen genetic message ~ in other words... Can a single gene code for more than one polypeptide? • Old virus inserts (?) • Way to create new proteins ~ increases chances for crossing over to occur... P.S. MY HEAD IS GOING TO EXPLODE WITH ALL OF THIS INFORMATION!! Alternative Splicing • The RNA can be spliced into different mRNA’s. • Each different mRNA produces a different polypeptide. 1965 Dictionary of Amino Acids mRNA
