2What do genes code for? How does DNA code for cells & bodies? DNA how are cells and bodies made from the instructions in DNADNAproteinscellsbodies
3DNA gets all the glory, but proteins do all the work! The “Central Dogma”Flow of genetic information in a cellHow do we move information from DNA to proteins?transcriptiontranslationDNARNAproteintraitTo get from the chemical language of DNA to the chemical language of proteins requires 2 major stages:transcription and translationDNA gets all the glory, but proteins do all the work!replication
4DNA mRNA protein trait From gene to protein nucleus cytoplasm aaFrom gene to proteinnucleuscytoplasmtranscriptiontranslationDNAmRNAproteinribosometrait
5from DNA nucleic acid language to RNA nucleic acid language Transcriptionfrom DNA nucleic acid language to RNA nucleic acid language
6DNA RNA RNA ribose sugar N-bases single stranded lots of RNAs uracil instead of thymineU : AC : Gsingle strandedlots of RNAsmRNA, tRNA, rRNA, siRNA…Small interfering RNA – involved in RNA interferencetranscriptionDNARNA
7Transcription Making mRNA transcribed DNA strand = template strand untranscribed DNA strand = coding strandsame sequence as RNAsynthesis of complementary RNA strandtranscription bubbleenzymeRNA polymerasecoding strand3AGCATCGT5AGAAAGTCTTCTCATACGDNAT3CGTAAT5GGCAUCGUT3CunwindingGTAGCArewindingmRNARNA polymerasetemplate strandbuild RNA 535
8Which gene is read? Promoter region Terminator region binding site before beginning of gene“Initiation” when RNA polymerase bindsElongation – mRNA madeTerminator regionSignals the end ofa gene.
9Matching bases of DNA & RNA Match RNA bases to DNA bases on one of the DNA strandsCUGAGUGUCUGCAACUAAGCRNApolymeraseU5'A3'GACCTGGTACAGCTAGTCATCGTACCGT
10Eukaryotic genes have junk! Eukaryotic genes are not continuousexons = the real geneexpressed / coding DNAintrons = the junkinbetween sequenceintrons come out!intron = noncoding (inbetween) sequenceeukaryotic DNAexon = coding (expressed) sequence
11mRNA splicing Post-transcriptional processing eukaryotic mRNA needs work after transcriptionprimary transcript = pre-mRNAmRNA splicingedit out intronsmake mature mRNA transcripteukaryotic RNA is about 10% of eukaryotic gene.intron = noncoding (inbetween) sequence~10,000 baseseukaryotic DNAexon = coding (expressed) sequencepre-mRNAprimary mRNAtranscript~1,000 basesmature mRNAtranscriptspliced mRNA
12from nucleic acid language to amino acid language Translationfrom nucleic acid language to amino acid language
13How does mRNA code for proteins? TACGCACATTTACGTACGCGGDNA4ATCGAUGCGUGUAAAUGCAUGCGCCmRNA4AUCG?Met Arg Val Asn Ala Cys Alaprotein20How can you code for 20 amino acids with only 4 nucleotide bases (A,U,G,C)?
14mRNA codes for proteins in triplets TACGCACATTTACGTACGCGGDNAcodonAUGCGUGUAAAUGCAUGCGCCmRNAAUGCGUGUAAAUGCAUGCGCCmRNA?Met Arg Val Asn Ala Cys Alaprotein
15The code Code for ALL life! Code is redundant Start codon Stop codons strongest support for a common origin for all lifeCode is redundantseveral codons for each amino acid3rd base “wobble”Why is the wobble good?Strong evidence for a single origin in evolutionary theory.Start codonAUGmethionineStop codonsUGA, UAA, UAG
16How are the codons matched to amino acids? 35DNATACGCACATTTACGTACGCGG53mRNAAUGCGUGUAAAUGCAUGCGCCcodon35UACMetGCAArgtRNACAUValanti-codonamino acid
17Transfer RNA structure “Clover leaf” structureanticodon on “clover leaf” endamino acid attached on 3 end
18Ribosomes Facilitate coupling of tRNA anticodon to mRNA codon organelle or enzyme?Structureribosomal RNA (rRNA) & proteins2 subunitslargesmallEPA
19Building a polypeptide 123Building a polypeptideInitiationbrings together mRNA, ribosome subunits, initiator tRNAElongationadding amino acids based on codon sequenceTerminationend codonLet’s watch it.LeuValreleasefactorSerMetMetMetMetLeuLeuLeuAlaTrptRNACAGCUAC5'UACGACUACGACGAC5'A5'UAAUGCUGAUAUGCUGAAUAUGCUGAAU5'AAUmRNAAUGCUG3'3'3'3'ACCUGGUAAEPA3'
20Can you tell the story? RNA polymerase DNA amino acids tRNA pre-mRNA exonintrontRNApre-mRNA5' GTP capmature mRNAaminoacyl tRNA synthetasepoly-A tail3'large ribosomal subunitpolypeptide5'tRNAsmall ribosomal subunitEPAribosome
21Mutations - Types Point Mutation – change in one base pair in a gene. SilentMissenseNonsenseFrameshift Mutation – results from an insertion (addition) or deletionMutagen – radiation, chemicals, usually carcinogenic