BIO1022 Lecture 1 â DNA Structure ⢠DNA and RNA runs from 5' to 3 ...
BIO1022 Lecture 1 – DNA Structure • DNA and RNA runs from 5’ to 3’ (‘ is A.K.A as “prime”) • Pyrimidines – T, C & U • Purines – A & G • DNA – Double stranded • RNA – Single stranded • Central Dogma: DNA à RNA à Protein (gene coding) • 3% of the genome is coding Copying DNA • Template: DNA used for the model for the RNA Non-Template/Coding: Not used as the messenger in translation and transcription • Promoter: Start of the sequence where the RNA polymerase starts (usually AUG) • TATA Box: Promotor recognises TATA Boxes to begin copying (in eukaryotes only) Eukaryotes Copying of DNA • Have introns and exons • Exons are the coding sequence and are kept (introns removed) • 5’ Cap added (allows to the exit nucleus) • Poly-A Tail added (extra protection) • Alternative Splicing: Different splicing of the same gene creates different mRNA and different protons
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Translation of RNA • tRNA (Transfer RNA): Brings in three bases (anticodon/foot) that code a section of RNA (binds to codon in mRNA) • Amino Acids are hooked and carried by tRNA • Uses the reduction of GTP to GDP to expend energy • A release factor binds the STOP codon, and the polypeptide chain is released (adds water instead of an amino acid) • mRNA is often translated by many ribosomes at once • In bacteria, transcription and translation can be coupled Mutations • DNA sequence differences arise due to mutation • All genes mutate spontaneously and randomly • Different levels of mutation: § Silent mutation § Mutation occurs but not evident on the sequence § Missense mutation § Amino acid does change § Nonsense mutation § Stops the polypeptide § Insertion/Deletion § Varied effects
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Causes of Mutations • Oxidative damage from normal cellular metabolism • Errors in the process of DNA replication or DNA recombination • 1 error for every 3 DNA replication events • Chemicals (tobacco, mutagens, etc.) • Radiation (UV, X-ray, gamma rays, etc.) • Polymorphisms: A continuum of mutations in a population Lecture 2 – Gene Regulation Trp Operon of E. Coli • Discovered in bacteria • Operant: Set of genes that sit together that are co-ordinately controlled • Used for metabolic pathways • Bacteria synthesise trp • In humans, trp is essential • Essential: Humans can’t produce the amino acid naturally • Operator: Can switch on/off the promoter • trpR is an independent gene that makes an inactive repressor • When there is no trp, there is no binding, therefore the operator allows the gene to be coded • Allosteric chemistry • Biosynthesis pathway
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Translation of RNA • tRNA (Transfer RNA): Brings in three bases (anticodon/foot) that code a section of RNA (binds to codon in mRNA) • Amino Acids are hooked and carried by tRNA • Uses the reduction of GTP to GDP to expend energy • A release factor binds the STOP codon, and the polypeptide chain is released (adds water instead of an amino acid) • mRNA is often translated by many ribosomes at once • In bacteria, transcription and translation can be coupled Mutations • DNA sequence differences arise due to mutation • All genes mutate spontaneously and randomly • Different levels of mutation: § Silent mutation § Mutation occurs but not evident on the sequence § Missense mutation § Amino acid does change § Nonsense mutation § Stops the polypeptide § Insertion/Deletion § Varied effects
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Causes of Mutations • Oxidative damage from normal cellular metabolism • Errors in the process of DNA replication or DNA recombination • 1 error for every 3 DNA replication events • Chemicals (tobacco, mutagens, etc.) • Radiation (UV, X-ray, gamma rays, etc.) • Polymorphisms: A continuum of mutations in a population Lecture 2 – Gene Regulation Trp Operon of E. Coli • Discovered in bacteria • Operant: Set of genes that sit together that are co-ordinately controlled • Used for metabolic pathways • Bacteria synthesise trp • In humans, trp is essential • Essential: Humans can’t produce the amino acid naturally • Operator: Can switch on/off the promoter • trpR is an independent gene that makes an inactive repressor • When there is no trp, there is no binding, therefore the operator allows the gene to be coded • Allosteric chemistry • Biosynthesis pathway
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