BIOL 1st Edition Lecture 23 Outline of Last Lecture I Cancer II Oncogenes and Proto Oncogenes III Tumor Suppressor Genes IV MicroRNAs Outline of Current Lecture I From Gene to Protein II Mutations III Split Genes and RNA Processing IV MicroRNAs and Gene Expression V Microbiology of Cancer VI Genetics of Viruses Current Lecture Overview of Material Covered Post Exam 3 I Chapter 17 Lecture 21 From Gene to Protein 1 What is the central dogma of molecular biology Define the terms transcription and translation The central dogma of molecular biology is the making of proteins Transcription is the synthesis of RNA from a DNA template Translation is the synthesis of proteins using information in the mRNA molecule 2 Define the terms for transcription Promoter the place where the RNA polymerase binds to on the DNA at the beginning of a gene RNA Polymerase the enzyme that makes RNA Transcription Factor the special proteins that guide the RNA polymerase to the promoter Terminator the place where transcription stops where the RNA polymerase releases the finished mRNA molecule and then falls off the DNA 3 Define the terms for translation mRNA RNA molecule that carries the coding information a series of codons that must be decoded one right after the other made of G C U and A Codon each 3 nucleotide code word that codes for some particular amino acid a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule Reading Frame a way of dividing the sequence of nucleotides in a nucleic acid DNA or RNA molecule into a set of consecutive non overlapping triplets Stop Codon don t code for anything but are signals to stop translation tRNA functions as a decoder that pairs the right amino acid with its codon Anticodon a sequence of three nucleotides forming a unit of genetic code in a tRNA molecule corresponding to a complementary codon in messenger RNA Ribosome small and large subunits organelle that coordinates the pairing of tRNAs with their mRNA codons separate except when translating mRNA into protein small binds to mRNA and special tRNA large binds to initiator tRNA in the P site P site large subunit of ribosome binds with initiator tRNA in the P site functioning ribosome A site a tRNA with correct anticodon for the next codon one after the start codon Release Factor binds in the a site this releases the protein ribosome separates into subunits ready to translate next mRNA 4 What are the mRNA structure terms Define them 5 Cap the cap that functions as a way for ribosomes to know where to attach 5 Untranslated Region the region between 5 cap and the start codon 3 Untranslated Region the region between the stop codon and the 3 end Poly A Tail attached to the 3 untranslated region stabilizes mRNA and regulates translation 5 Understand the sequence of events and briefly what happens during initiation elongation and termination of translation movie Sequence Initiation Elongation Termination Initiation small ribosomal subunit is base paired to an initiator tRNA and moves to the initiation site large ribosomal subunit attaches to the tRNA which is attached to the small ribosomal unit creating the p site Elongation a second tRNA enters the a site bonded with a peptide bond to the first tRNA the methionine is transferred to the a site amino acid the first tRNA exits the third tRNA enters and the second tRNA moves along etc Termination when a stop codon is encountered a release factor enters the a site and translation is terminated the newly formed protein detaches and the ribosome separates into subunits ready to translate again 6 Given a codon determine the anticodon of the tRNA that would bind to it Base pairing rules for mRNA codons to tRNA U to A A to U C to G G to C Example Given 5 AUG 3 the anticodon would be 3 UAC 5 II Mutations Lecture 21 7 What is a mutation Mutations are changes in the nucleotide sequence in DNA 8 Name two basic classes of mutation The two basic classes of mutations are base pair substitutions and insertions deletions Base pair substitutions occur when a nucleotide pair is replaced by another Insertions deletions occur when one or more nucleotide pairs are inserted or deleted from a gene 9 What is a missense mutation What is a nonsense mutation Which of these is generally more serious A missense mutation alters a codon in a gene but the new codon still codes for an amino acid Depending on how different the new amino acid is and where it is located determines whether this mutation is lethal or harmless A nonsense mutation is when a codon is changed into a stop codon which stops translation prematurely Nonsense mutations are significantly more serious because they prematurely stop translation from occurring 10 What is a frameshift mutation A frameshift mutation occurs when the number of nucleotides inserted or deleted is in multiples of 3 III Split Genes and RNA Processing Lecture 21 11 Is most DNA in eukaryotes coding or non coding Most DNA in eukaryotes is non coding 12 What is an exon What is an intron An exon is a coding region within the DNA that carries the code for how to make a protein An intron is a non coding region within the DNA that does not encode a protein 13 What happens during RNA splicing What is the name of the complex particles that carry out RNA splicing Where in the cell does RNA splicing occur RNA splicing occurs after transcription and it is the process of removing the introns from the mRNA and hooking the exons back together Spliceosomes carry out the process of RNA splicing RNA splicing occurs in the nucleus of a cell 14 Name three processing steps that must occur to produce the mature mRNA from a gene that has introns The three processing steps that must occur to produce the mature mRNA from a gene that has introns are RNA splicing the addition of a 5 cap and the addition of a 3 poly A tail IV MicroRNAs and Gene Expression Lecture 21 15 What is meant by gene expression Gene expression or expressed genes are when a gene is actively being used to make proteins through transcription and then translation 16 What is meant by transcriptional control and post transcriptional control Transcriptional control is the control of gene expression by determining which genes are transcribed when they are transcribed and how often they are transcribed Post transcriptional control is the control of gene expression at the RNA level which occurs between the transcription and translation processes 17 What is a microRNA MicroRNAs are a