BIOL10221 Molecular Biology Lecture Notes PDF

BIOL10221 “Molecular Biology” Dr David Boam Module 4 - From DNA to RNA Lecture 1: Genes, polymerases and  Aims for this lecture To compare gene structure in prokaryotes and eukaryotes To describe and explain the principle features of transcription RNA polymerase b...

BIOL10221 “Molecular Biology” Dr David Boam Module 4 - From DNA to RNA Lecture 1: Genes, polymerases and  Aims for this lecture To compare gene structure in prokaryotes and eukaryotes To describe and explain the principle features of transcription RNA polymerase basic function Sense/antisense coding/noncoding DNA strands Nucleotide structure and transcription BIOL10221 lecture 4/1 Transcriptional regulation DNA Genes Transcription RNA Translation Protein BIOL10221 lecture 4/1  Nature and Structure of Genes What is a gene? A genetic unit containing information to make a functional product (RNA and/or Protein) What information does a gene contain? 1) Structural - coding DNA 2) Temporal (developmental) 3) Positional (tissue/cell specific) 4) Inducible (nutrients, stress, hormones) BIOL10221 lecture 4/1  Prokaryotic gene organisation spacer Transcription Coding regions (cistrons) Leader start terminator -X +1 +X Promoter - defines transcription start site and it's direction Transcriptio Leader/spacer - n Polycistronic section of DNA which is mRNA nontranslated AUG UGA Cistron - segment of DNA corresponding to Translation one polypeptide (protein) polypeptides Note transcription start/stop sites are not the same as translation start/stop sites!! BIOL10221 lecture 4/1  Eukaryotic Class II (mRNA-encoding) genes Transcription start Transcribed region ATG TGA Enhancer Promoter Intron Regulatory elements Exons Promoter mature mRNA AUG UGA Enhancer – sometimes distal from promoter, 5'-UTR Translate 3'-UTR contains transcription d region factor binding sites Nucleus COOH Cytoplasm H2N Intron - in primary transcript but removed from mature transcript Exon - in mature transcript UTR - Untranslated regionBIOL10221 lecture 4/1  Size of prokaryotic and eukaryotic genes Eukaryotic genes can be quite large ~50kB Most is non-coding Lower eukaryotic and prokaryotic genes are small and equate more to the size of polypeptides they produce BIOL10221 lecture 4/1  General Mechanism of Transcription The DNA that contains a gene is made up of: Coding strand (sense) 5’ - 3’ Has same sequence as RNA product Template Strand (antisense) 3’ - 5’ Sequence is complementary to RNA product Coding Strand (sense) 5’ 3’ 3’ 5’ Template strand (antisense) BIOL10221 lecture 4/1 Making sense of sense and antisense 5' AU mRNA CG UU (copy of (same sequence as) AU coding strand, complementary GC GC to non-coding strand) UU AG GC CC... 3'... Sense or coding strand 5 ATCGTTATGCGCTTAGGCCC............................. 3' ' 3' TAGCAATACGCGAATCCGGG........................... 5' Antisense, template or non-coding strand RNA polymerase BIOL10221 lecture 4/1  Lets talk about promoters How does the RNA polymerase know where and when : 1) …. to bind to DNA? 2) …. Which direction to start transcription? -35 -10 TTGACA TATAAATG “Pribnow” Box +1 3’-AACTGT…..ATATTTAC-5’ BIOL10221 lecture 4/1  Transcription “Bubble” RNA Polymerase (Sense) Coding Strand 5’ 3’ 3’ 3’ 5’ Template Strand (Antisense) 5’ Nascent RNA RNA polymerase binds to DNA melts double strand, polymerises 5’ to 3’ direction RNA produced is copy of the coding strand and complementary to template strand BIOL10221 lecture 4/1  RNA Polymerase (Sense) Coding Strand 5’ 3’ 3’ 3’ 5’ Template Strand (Antisense) 5’ Nascent RNA How does the RNA polymerase know where : 1) ….and when to bind to DNA? 2) …. and when to start transcription? 3) to stop transcription? All this information is found in the gene! BIOL10221 lecture 4/1  Genes summary All genes contain a regulatory element - promoter/enhancer – direction – position – spacial/temporal/inducibility prokaryotic genes differ in organisation and function from eukaryotic – cistrons vs introns/exons Next lecture.... The transcription machinery in prokaryotes and eukaryotesBIOL10221 lecture 4/1  Genes summary All genes contain a regulatory element - promoter/enhancer – direction – position – spacial/temporal/inducibility Prokaryotic genes differ in organisation and function from eukaryotic – Cistrons/spacers vs introns/exons BIOL10221 lecture 4/1  Intended learning outcomes You should Keywords Have a basic understanding of prokaryotic and eukaryotic gene structure and how they differ from Sense and each other antisense Have a basic understanding of the Coding/non- process of transcription and the coding role of RNA polymerase in this template process RNA polymerase Understand the concept of sense Promoter and antisense in the context of transcription Intron Understand the how structure of Exon nucleotides is important to UTR transcription at the molecular level Spacer Leader Cistron BIOL10221 lecture 4/1