Lecture 12 Outline of Last Lecture 1. Endocytosis 2. Mitochondria 3. Endosymbiosis4. Central DogmaOutline of Current Lecture 1. Transcription2. Sigma Factor3. Regulation of Protein Synthesis & Metabolism4. TranslationCurrent LectureTranscription- Use DNA as template, make RNA No T’s in RNA, there are U’s.- -10 / -35 : Distance from first nucleotide that needs to be transcribedSigma factor- Only prokaryotes have this. Bacterial. What recognizes the -10 & -35 to align the polymerase to bind. To synthesize transcript.3 Steps of Transcription1. Initial- Opens up DNA, starts copy from template strand.2. Elongation- Finish copying3. Terminate- Ending of copying. Don’t want to go beyond site of transcription.One transcript for each gene- ONLY in eukaryotes. One geneOne messenger RNAPolycistronic- Only Prokaryotes: multiple genes in same transcriptional region- Promoters site=P. Real terminator site= tOperon- series of genes, tightly controlled with some related functionWhat determines amount of RNA?1. How often do you initiate transcription?- More frequent= more there are BSC 160 1nd Edition2. How fast is your polymerase?3. Strong promoters- Transcribed often. Binds tightly to sigma factorWeak promoters- Less transcription4. Repressors & Enhancers- Turn on and off - Repressors- Block promoters, stop transcription- Enhancers- CAP helps RNA polymerase bind correctly to transcription locationRegulation of Protein Synthesis & Metabolism- Genes are regulated to be active only when their products are required- In prokaryotes, this regulation is coordinated by operons, a set of genes, all of which are regulatedas a single unitLactose Operon: Inducible Operon. Normally off position.Arginine Operon: Repressible. Always on positionEnterons- Only eukaryotes: Extra DNATranslation-- Each triplet of nucleotides on the RNA specifies a particular amino acid- A protein’s structure determines its shape & function- Proteins determine phenotype. Living things are what their proteins make them- DNA is mainly a blueprint that tells the cell which kinds of proteinMessenger RNA (mRNA)- Carries DNA message through complimentary copy; message is in triplets called codonsTransfer RNA (tRNA)- Secondary structure creates loops; bottom loop exposes a triplet of nucleotides called anticodon, which designates amino acid complement mRNA; carries specific amino acid to ribosomesRibosomal RNA (rRNA)- Component of ribosomes where protein synthesis occursPolyribosomal complex- Allows for the synthesis of many protein molecules simultaneously from the same mRNA
View Full Document
Unlocking...