BIO1204 Lecture - Genes to Organisms PDF

BIO1204 Introduction to Biomedical Science Genes to Organisms  The material in this lecture and course should be not uploaded or shared on any online platform outside of the University of Southern Queensland....

BIO1204 Introduction to Biomedical Science Genes to Organisms  The material in this lecture and course should be not uploaded or shared on any online platform outside of the University of Southern Queensland. COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been copied and communicated to you by or on behalf of The University of Southern Queensland pursuant to Part VA of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further copying or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. 2  Acknowledgement of Country In the spirit of reconciliation, the University of Southern Queensland acknowledges the traditional custodians of the lands and waterways where the University is located. Further, we acknowledge the cultural diversity of Aboriginal and Torres Strait Islander peoples and pay respect to Elders past, present and future. 3  Learning Outcomes To be able to: – Explain the flow of information from DNA to proteins, including mRNA processing in eukaryotes. – Compare the difference in gene organisation between prokaryotes and eukaryotes. – Explain the types of regulation for eukaryotic genes. – Define “genome” and be able to discuss the human genome project. 4  Gene definition The unit of genetic information that controls a specific aspect of phenotype –Specifies the synthesis of one polypeptide »Now refined to include RNA molecules that will never be polypeptides……… 5  Genes form organisms Although DNA is the same molecule in all organisms, the way that the DNA is arranged as ‘genes’ differs between organisms and individuals within organism groups 6  The Flow of Genetic Information DNA contains genetic information organised as genes on chromosomes Genetic information or DNA sequence (AACGG...etc) is transcribed to RNA molecules RNA molecules carry the information out of the nucleus RNA information is translated into a protein Proteins perform the majority of biological functions – DNA contains instructions to produce RNA/proteins to replicate (copy) itself – Genetic information is passed to future generations 7 mRNA – Specifies the Amino Acid Sequence *Eukaryotic cell DNA mRNA Protein “Central Dogma” 8  The Human Genome Project Proposed in 1990 as $multi-billion joint venture with 15 year completion goal Celera Genomics began in 1998 In 2000, working ‘draft’ of human genome announced (95% complete) Draft sequence published in 2001 Work completed in April 2003 (only ~300bp small gaps remaining), 3 billion bp sequenced, 21,000 protein-coding genes http://www.ornl.gov/sci/techresources/Human_Genome /home.shtml 9 Sizes of other Genomes 10  Molecular Definition of a Gene Entire nucleic acid sequence that is necessary for the synthesis of a functional polypeptide or RNA molecule Includes: –5’ regulatory sequences (eg. promoters) –3’ regulatory sequences (eg. termination sequences) –Coding region (exons) –Introns (if Eukaryotic cells) 11  Prokaryote Gene Regulation of translation Signals for Regulation termination of transcription of transcription Primary transcript Polypeptide Snustad & Simmons Uninterrupted coding sequences – no introns Operons Polycistronic mRNA - encodes multiple genes 12  Eukaryote Gene Regulation of translation Signals for termination Regulation of transcription of transcription Primary transcript mRNA Polypeptide Snustad & Simmons 13  Gene Organisation Differences Prokaryote vs Eukaryote Polycistronic Operons Monocistronic genes Genes are relatively Genes are usually ‘well ‘crowded’ in the genome spaced’ in genome No introns Introns present 14  Bacterial genomes Operons – A group of genes that comprise a regulatory/control unit 15  Trp Operon in E.coli The trp operon contains 5 structural genes that encode enzymes for tryptophan biosynthesis A single transcription control region produces a single polycistronic mRNA for 5 genes Translation may commence at the start of any of the 5 genes in this polycistronic mRNA However, a mutation in the control region of the single transcript will affect the production of all 5 proteins that it encodes 16  Trp Operon in E.coli If tryptophan is present, it binds the repressor & activates it – negative repressor – No transcription 17  Regulation of Eukaryotic Gene Expression Spatial specificity – Tissues & organs Temporal specificity – Sequence of expression, in response to cues Transcription regulation – Transcription factors (TFs) interact with DNA Alternative splicing of RNA 18  Generalised Structure of a Eukaryote Gene DNA organised in genes Genes can comprise – Exons (expressed regions) Code proteins Required in mRNA – Introns (intervening regions) In vast majority of eukaryotic genes & some rRNA & tRNA genes Transcribed but not translated Removed by splicing of the pre-mRNA 19  Generalised Structure of a Eukaryote Gene ATG (Met start) TAG (Stop) 5’ Regulatory region 3’ Regulatory region Exon 1 Intron Exon 2 Intron Exon 3 Cleavage & Transcription Start Polyadenylation Splice Junctions = Sequences that recognise transcription factors = Sequences regulate rates of transcription = 5’ & 3’ untranslated regions (UTR) are part of the 1st & last exons 20  Non-Coding Sequences Non-translated regions Introns (intervening sequences) Not present in the mRNA Unique to Eukaryotic genes Up to 70,000 nucleotide pairs in length Removed by RNA splicing 21  Introns – Why? Regulate expression? Relic? Assist recombination? 22  Alternative Splicing Generates different proteins from a single gene Different splice sites 23  RNA Processing - putting it all together.......  At the 5’ EXON 1 5’ UTR end of the β-globin gene... INTRON 1 EXON 2 Transcription Start Site INTRON 2 ATG Translation Start (Met) the β-globin gene sequence Intron Boundaries 25  5’ UTR EXON 1 The green line surrounds the sequence of the DNA that will be transcribed INTRON 1 Coding regions are shown with a red background Introns & UTRs are shown with a blue EXON 2 background INTRON 2 Transcription Start Site the β-globin gene sequence ATG Translation Start (Met) Intron Boundaries 26  At the 3’ end of the gene.... INTRON 2 The green line surrounds the sequence of the primary transcript Exons are shown with a red background EXON 3 Introns are shown with a blue background 3’ UTR AATAAA is the cleavage & polyadenylation signal From Alberts "Mol Biol of the Cell" 27  Lecture Summary Genes are the unit of inheritance The flow of information to form organisms is from DNA (genes) to RNA to polypeptides (proteins) The genes in an organism form its genome Human genome project sequenced ~21,000 genes (not all identified) Prokaryote & eukaryote genes differ in complexity – Operons in prokaryotes, introns, UTRs, Regulation of genes in eukaryotes – Transcription factors – Alternative splicing 28  References Campbell, Reece & Meyers, 2006 Biology 7th Edition, Benjamin Cummings Publishing. Snustad & Simmons, 2004 Principles of Genetics 2nd Edition, Wiley Publishing. Mathews & Van Holde, 1990 Biochemistry, Benjamin Cummings Publishing. Lodish, Berk, Matsudaira, Kaiser, Krieger, Scott, Zipursky & Darnell, 2004 Molecular Cell Biology 5th Edition, WH Freeman Publishing. 29  Practice exam questions – Part A 1. Which of the following is NOT a characteristic of a prokaryotic gene? A. Contains regulatory promoter and termination regions B. Related genes grouped in operons C. Expression regulation by gene product D. Polycistronic mRNA E. mRNA processing to remove introns 30  Practice exam questions – Part A 1. Which of the following is NOT a characteristic of a prokaryotic gene? A. Contains regulatory promoter and termination regions B. Related genes grouped in operons C. Expression regulation by gene product D. Polycistronic mRNA E. mRNA processing to remove introns 31  Practice exam questions – Part B 1. Describe the types of regulation for eukaryotic gene expression. 32  Any questions? - Post on the StudyDesk forum (if you have question, someone else will too!) - Can also email [email protected] 33 34