* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download DNA Replication - Texas Tech University
Gel electrophoresis wikipedia , lookup
Community fingerprinting wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Alternative splicing wikipedia , lookup
X-inactivation wikipedia , lookup
Gene regulatory network wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Genetic code wikipedia , lookup
Transcription factor wikipedia , lookup
Molecular evolution wikipedia , lookup
Real-time polymerase chain reaction wikipedia , lookup
Biosynthesis wikipedia , lookup
RNA interference wikipedia , lookup
Non-coding DNA wikipedia , lookup
Promoter (genetics) wikipedia , lookup
Messenger RNA wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Polyadenylation wikipedia , lookup
Deoxyribozyme wikipedia , lookup
RNA silencing wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Gene expression wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Transcription AHMP 5406 Objectives: 1. Describe the general process of DNA transcription 2. Discuss the function of RNA polymerases 3. Differentiate between messenger RNA, small nuclear RNA, ribosomal RNA, and transfer RNA 4. Explain the purpose of the promoter and terminator 5. Compare and contrast the three types of RNA polymerase in eukaryotic nuclei: RNA polymerase I, RNA polymerase II, and RNA polymerase III 6. Discuss RNA capping & RNA splicing 7. Explain the selective exportation of mRNAs from the nucleus 8. Discuss ribosomal RNA and its function What is Transcription ? DNA does not direct protein synthesis directly RNA is used as intermediate Transcription = Copying DNA into RNA RNA Ribonucleic Acids Contain ribose instead of deoxyribose (DNA) Polymers formed by A, G, C, and U U = uracil Complementary to Thymine But sometimes binds to G Single stranded Can bind to itself and form 3D structures DNA to RNA Transcribed RNA is complementary to 1 DNA strand Transcribe RNA = transcript Transcripts can only reach a few thousand bases in length Unidirectional 5’-3’ RNA Types Coding Messenger RNA (mRNA) Non-coding Ribosomal RNA (rRNA) Transfer RNA (tRNA) Small nuclear RNA (snRNA) Small nucleolar RNA (snoRNA) mRNA Codes for proteins Can be modified by splicing, 5’ and 3’ additions Non-Coding RNAs rRNA Form basic structure of ribosome tRNA Adaptors b/w mRNA and AA snRNA Several nuclear processes Assist in splicing snoRNA Process and chemically modify rRNA DNA sequences used as signals Sequences signal transcription to start and stop Promoters – start signals s factor binds to promoter in bacteria Terminators – stop signals In bacteria A-T region causes fold RNA polymerases RNA pols perform transcription Immediate release of transcript allows many RNA to be synth. in a short time More error prone than DNA pols They have limited error correction abilities Types of RNA polymerases RNA pol I Transcribe 5.8S, 18S and 28S genes S = Svedberg units, sedimentation coefficient related to centrifugation The bigger the number the bigger the molecule RNA pol II Transcribe protein-coding genes, snoRNA genes Some snRNA genes RNA pol III Transcribe tRNA genes and some snRNA genes Transcription in Euks. Requires general transcription factors to initiate transcription GTFs help position RNA pol II correctly TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH Recognize specific sites on DNA RNA pol start points TATA Box promoter Recognized by subunit of TFIID TBP – TATA Box Binding protein approx 25 bp upstream of initiation point Causes conformational change in DNA Other necessary proteins for initiation of transcription Transcriptional activators Attract RNA pol II to start site Mediators Allow communication between activator and GTFs Chromatin remodeling proteins Modify DNA conformation Elongation Factors Increase affinity of RNA Pol II to DNA Assist in moving through chromatin structure mRNA modifications 5’ capping Splicing = removing introns 3’ Polyadenylation 5’ Capping When RNA Pol II at 25 bases 5’ cap is added to transcript Modified guanine Three enzymes Phosphatase = removes phosphate from 5’ end Guanyl transferase = adds GMP Reversed linkage 5’-5’ Methyltransferase = adds methyl group to guanosine Splicing Removes introns (or sometimes shuffling) Sequences signal where to cut Spliceosome performs cutting Complex of snRNAs (Us) and protein Self Splicing Mechanisms Group I Bind free G nucleotide to specific site Group II Uses reactive A nucleotide Unusual mechanisms Poly A tail Cleavage stimulating factor F (CstF) Cleavage and polyadenylation specificity factor (CPSF) Export of mRNA Goes through nuclear pore complexes Mature mRNA are modified and protein bound Signal (passport) for transport of mRNA outside of nucleus 5’ cap proceeds first rRNAs Transcribed by RNA Pol I rRNAs are made from a larger precursor Sections are modified, cleaved and assembled into ribosomes in nucleolus Subnuclear structures Sites where snRNA processing machinery is assembled, stored and recycled Cajal bodies GEMS (Gemini of coiledbodies) Interchromatin granule structures