Week 3: Transcription
Week 3: Transcription Bio 107
Popular in Biology
verified elite notetaker
Popular in Biology
This 6 page Class Notes was uploaded by Rachel Johnson on Tuesday September 15, 2015. The Class Notes belongs to Bio 107 at Washington State University taught by William Davis in Summer 2015. Since its upload, it has received 40 views. For similar materials see Biology in Biology at Washington State University.
Reviews for Week 3: Transcription
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/15/15
Transcription I Gene Expression the use of DNA to make a final product Central Dogma of Biology 393 States that information ows in a speci c way DNA gt RNA gt Protein DNA is transcribed into mRNA mRNA is translated into protein Triplet Code 0 Codon a grouping of three nucleotides that specify one amino acid 393 Genetic code redundancy there can be more than one codon for an amino acid Start codon AUG methionine Stop codons UAA UAG UGA Discovery Artificial Resulting amino mRNA acids gt Lots of bacterial gt AAA ribosomes Lysme UUU Phenylalanine CCC Proline GGG Glycine Was experimentally determined through this method Later veri ed by comparing DNA mRNA and protein sequences Transcription 0 RNA synthesis by a RNA polymerase 0 The leading DNA strand is used as a template template strand or coding strand and the other strand is simply a bystander 0 3 stages Initiation Transcription always begins at a promoter a speci c DNA sequence Transcription factors bind to the promoter and recruit the RNA polymerase Elongation RNA polymerase synthesizes RNA in the 5 gt 3 direction reads the leading strand in the 3 gt 5 direction Doesn t require a primer Uses nucleoside triphosphate as substrates Termination In prokaryotes involves termination sequences In eukaryotes associates with RNA processing Transcription II mRNA in Prokaryotes 0 There is no nucleus Chromosome and ribosomes are in the cytoplasm 0 mRNA is translated into protein as soon as it is transcribed mRNA in Eukaryotes 0 There is a nucleus mRNA is made in the nucleus Ribosomes are in the cytoplasm 0 mRNA must be transported from the nucleus to the cytoplasm mRNA Processing in Eukaryotes 0 PremRNA is made in the nucleus and is modi ed into mature mRNA Modi cation occurs before the RNA is exported from the nucleus 393 5 end capping Functions Addition of a methylated guanine gt mRNA Xp0rt RNA t b39l39t 0 3 end polyadenylation m S a 1 1 y mRNA translation Addition of a polyA tail 0 UTR untranslated region Regions occurring right after the 5 end and right before the 3 end Contains essential sequences for translation RNA Splicing in Eukaryotes 0 Removes intervening sequences introns 0 Unites exported sequences exons Segments of the mRNA that will actually get translated into protein 03 Functions Facilitates the export of the mRNA from the nucleus Allows for multiple proteins to be made from the same gene 03 Process The branch site in an intron is a speci c RNA sequence that attacks the donor site at the upstream boundary between the intron and exon Produces a loop that curls back over itself a 1ariat The upstream exon attacks the acceptor site on the nearest downstream intron to release the exon from the mRNA Gel Electrophoresis of RNA 03 Load RNA onto a gel lled tray at the negative end and run an electrical current through it 393 The distance traveled from the loading site shows the size of the RNA The bigger the molecule the shorter the distance traveled Transcription Regulation and RNA Interference Eukaryotic Genes 0 Contain control elements Sequences that regulate transcription of DNA Bound by transcription factors that help form proteins Transcription Factors TFs 0 General TFs used for all proteincoding genes 393 Specific TFs used for a set of proteincoding genes Required for high levels of transcription Transcription Activation 0 Can occur over long distances Assisted by DNAbending proteins 03 Many interactions help initiate Transcription Repression 0 Transcription can be shut down 03 Works in a similar fashion to activation DNA transcription factor binding sequences called silencers DNAbinding proteins called repressors RNA Interference 0 Used in labs to disable specific genes to determine their function