The Central Dogma and RNA Transcription
The Central Dogma and RNA Transcription Bsci105
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This 0 page Class Notes was uploaded by Trang Le on Friday November 6, 2015. The Class Notes belongs to Bsci105 at University of Maryland taught by Dr. Alewall in Summer 2015. Since its upload, it has received 71 views. For similar materials see Intro to biological sciences in Biological Sciences at University of Maryland.
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Date Created: 11/06/15
THE CENTRAL DOGMA AND RNA TRANSCRIPTION The central dogma of biology states that genetic information ows from DNA to RNA to protein DNA template 3 5r strand ACCAAACCGAGT 5 MIL 3r TGGTTTGGGTCA I THANSCF IIPTI ON Protein Tirp Amino acid Central dogma There are differences in pathway from gene to protein between prokaryotes and eukaryotes Unigue features of eukaryotes The DNA in chromatin is highly packaged RNA is transcribed in the nucleus but translated in the cytoplasm It eXits the nucleus through nuclear pores The transcript pre RNA contains large noncoding regions introns that are spliced out in nucleus RNA processing All of these steps are highly regulated The regulation plays a major role in the regulation of gene expression RNA is transcribed from the template strand of DNA by RNA polymerase in a process similar to DNA replication Transcription has three phases initiation elongation and termination Initiation begins at a specialized DNA sequence called a promoter Elongation is the template directed addition of ribonucleotides to the growing RNA chain Termination occurs at specialized DNA sequences Eukaryotic RNA undergoes post transcriptional modifications capping and splicing Like DNA mRNA is synthesized in the 5 gt3 direction The nucleotides in RNA are ribonucleotides with ribose as the sugar The base in RNA that is complementary to A is U not T The reaction is catalyzed by RNA polymerase which also opens the DNA double heliX Triplets of nucleotides codons code for amino acids Three important components of RNA transcription RNA polymerase promoter and termination signal RNA polymerase analogous to DNA polymerase helicase Promoter Site on DNA where transcription is initiated Transcriptional initiation requires a TATA box within the promoter and several proteins called transcription factors The complete compleX of RNA RNA polymerase and the transcription factors is called the transcription initiation complex Termination signal specific DNA sequence that signals termination Called the polyadenylation signal Transcriptions ends 10 35 bases downstream 3 to 5 direction Promoter Transcription unit 3r r r 5 1 Start point 7 RNA ol merase 0 Initiation p y 5r 2 I 3 3 WAT I 5 unwound 39 RNA Template strand at DNA DNA transcript 9 Eton ation g Pewound 5r X 3r 5 3r 1 t 5397 t Direction of FINA transcription i i transcript downstream 0 Termination 739 539 a i 3 3 i j a 5 539 i 3quot Complieted RNA transcript Termination in prokaryotes and eukaryotes Prokaryotes a special sequence called the terminator is transcribed and folds into 03 2014 Pearson Education Inc a hairpin This causes RNA polymerase to pause and then release DNA and RNA Eukaryotes The sequence AAUAAA polyadenylaton signal signals termination although transcription proceeds for 10 25 more nucleotides before the RNA is released Further processing of the 3 tail occurs later The genetic code Enables the sequence of amino acids in proteins to be encoded in nucleic acids Amino acids are specified by sequences of three nucleotides which are called codons Since there are 64 combinations of 3 nucleotides most amino acids are specified by more than one codon Three codons UAG UAA UGA do not specify amino acids but instead designate the end of the protein sequence stop codons The codon AUG specifies the translational initiation point start codon and codes for the amino acid methionine Second mFiNA base E E 3 E 3 u Ii 0 C O 5 C Leu I Pro I f n Arg u CUA 39CCA 39CAA quotCGA A E D 39 Gin quot m in CUG CCG E CAG E i CGGI G g a 77 l as s I 4 3 AUU Acu 395 AAU AGU U 3 m I 7 Asn u Ser 7 g 4 A Thr I n E Z AUA I ACA I AAA quotAGA A D I I Lvs n Ara g E AUG 33 ACG AAG gAGG a E T T39 2 if GUIU GCU GAU A EGGU U IE 5 GUC Gcc GAc paac c G Val Aia n Gly GUA IGCA IGAA Gm HGGA A I I n GUG GCG quotGAG GGG G 2014Pearson Educatioan DNA Promoter Nontemplate strand 5 3 A eukaryotic 3 f 5 promoter TATA box Start point Template strand Transcription GSeveral transcription factors bind to DNA Transcription factors 3 9 Transcription initiation RNA transcript gaggle Transcription initiation complex Initiation in Eukaryotes Promoter Transcription unit RNA polymerase 0 Initiation 539 3r 339 5 Unwound RNA Template strand of DNA DNA transcript Elon ation 9 g Flewound 5 3 0 Termination Q 201 4 Fee rsnn Education m 5 3 Direction of transcription transcrlpt 5 Completed RNA transcript Termination downstream gt Transcription in Prokaryotes
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