Division Ave. High School AP Biology

Transcription

1 Division ve. High School Making s From ene to Protein How enes Work Organelles nucleus ribosomes endoplasmic reticulum (ER) olgi apparatus vesicles small nuclear pore ribosomal mrn large ribosomal cytoplasm Nucleus & Nucleolus Nucleolus Function ribosome production build ribosome s from rrn & s exit through nuclear pores to cytoplasm & combine to form functional ribosomes large small rrn & s ribosome nucleolus Ribosomes Function production Structure rrn & 2 s combine Ribosomes Rough ER large small 0.08µm ypes of Ribosomes Free ribosomes suspended in cytosol synthesize s that function in cytosol Bound ribosomes attached to endoplasmic reticulum synthesize s for export or for membranes Smooth ER membrane s PDF reated with deskpdf PDF Writer - rial :: 1

2 Division ve. High School DN nucleus RN endoplasmic reticulum vesicle on its way! O: O: O: End of the our O: vesicle ribosomes O: finished Making Proteins olgi apparatus What happens in the cell when a gene is read? Where are the genes? Y Where does a gene start? Where does the gene end? from DN? How is one gene read and another one not? How do s create phenotype? How do cells make s abolism taught us about genes Inheritance of metabolic diseases metabolic pathway suggested that genes coded for enzymes each disease (phenotype) is caused by non-functional gene product lack of an enzyme ay sachs PKU (phenylketonuria) albinism m I just the sum of my s? disease disease disease disease B D E enzyme 1 enzyme 2 enzyme 3 enzyme 4 Beadle & atum one gene : one enzyme hypothesis One gene / one enzyme hypothesis Damage to specific gene, mapped to nutritional mutations chromosome gene cluster 1 arg-e gene cluster 2 arg-f gene cluster 3 arg- arg-h eorge Beadle encoded enzyme enzyme E enzyme F enzyme enzyme H Edward atum "for their discovery that genes act by regulating definite chemical events" glutamate ornithine citruline arginosuccinate arginine substrate in gene that P biochemical Biology pathway was damaged PDF reated with deskpdf PDF Writer - rial :: 2

3 Division ve. High School he entral Dogma Flow of genetic information in a cell DN How do we move information from DN to s? replication transcription RN translation DN gets all the glory, but s do all the work! trait RN ribose sugar N-bases uracil instead of thymine U : : single stranded lots of RNs mrn, trn, rrn, sirn DN transcription RN ranscription from DN nucleic acid language to RN nucleic acid language ranscription Making mrn transcribed DN strand = template strand untranscribed DN strand = coding strand same sequence as RN synthesis of complementary RN strand transcription bubble enzyme coding strand RN polymerase 5 DN 3 rewinding mrn 5 build RN 5 3 U RN polymerase 3 U 3 5 unwinding template strand ranscription in Prokaryotes Psssst no nucleus! ell membrane ell wall Bacterial chromosome ranscription mrn ranscription in Prokaryotes Initiation RN polymerase binds to promoter sequence on DN Role of promoter Starting point where to start reading start of gene emplate strand which strand to read Direction on DN always read DN 3 5 P Biology build RN 5 3 PDF reated with deskpdf PDF Writer - rial :: 3

4 Division ve. High School enzyme ranscription in Prokaryotes read DN 3 5 Promoter sequences Promoter RN polymerase 35 sequence 10 sequence RN polymerase bacterial DN RN polymerase molecules bound to bacterial DN strong vs. weak promoters ranscription in Prokaryotes Elongation RN polymerase copies DN as it unwinds Simple proofreading 1 error/10 5 bases make many mrns mrn has short life not worth editing! ~20 base pairs at a time bases in gene builds RN 5 3 reads DN 3 5 ranscription in Prokaryotes ermination RN polymerase stops at termination sequence ranscription in Eukaryotes RN hairpin turn Psssst DN can t leave nucleus! ranscription RN Processing ranslation Protein Prokaryote vs. Eukaryote genes Prokaryotes eukaryotic DN DN in cytoplasm circular chromosome naked DN no introns Eukaryotes DN in nucleus linear chromosomes DN wound on histone s introns vs. exons intron = noncoding (inbetween) sequence exon = coding (expressed) sequence introns come out! ranscription in Eukaryotes 3 RN polymerase enzymes RN polymerase 1 only transcribes rrn genes makes ribosomes RN polymerase 2 transcribes genes into mrn RN polymerase 3 only transcribes trn genes each has a specific promoter sequence it recognizes PDF reated with deskpdf PDF Writer - rial :: 4

5 Division ve. High School ranscription in Eukaryotes Initiation complex transcription factors bind to promoter region upstream of gene suite of s which bind to DN turn on or off transcription box binding site recognition site for transcription factors transcription factors trigger the binding of RN polymerase to DN Post-transcriptional processing Primary transcript (pre-mrn) eukaryotic mrn needs work after transcription mrn processing (making mature mrn) mrn splicing = edit out introns protect mrn from enzymes in cytoplasm eukaryotic DN primary mrn transcript add 5 cap add poly tail mature mrn transcript cap PPP exon = coding (expressed) sequence mrn intron = noncoding (inbetween) sequence pre-mrn poly- tail s ~10,000 bases ~1,000 bases spliced mrn Bacterial chromosome ranslation from nucleic acid language to amino acid language ranslation in Prokaryotes Psssst no nucleus! ranscription ranslation mrn ell membrane ell wall ranslation in Prokaryotes ranscription & translation are simultaneous in bacteria DN is in cytoplasm no mrn editing ribosomes read mrn as it is being transcribed ranslation: prokaryotes vs. eukaryotes Differences between prokaryotes & eukaryotes time & physical separation between processes takes eukaryote ~1 hour from DN to RN processing PDF reated with deskpdf PDF Writer - rial :: 5

6 Division ve. High School ranslation in Eukaryotes From gene to DN transcription mrn leaves nucleus through nuclear pores mrn translation ribosome nucleus cytoplasm s synthesized by ribosomes using instructions on mrn How does mrn code for s? DN 4 mrn 4 20 U U U UU U? rg Valsn lays la How can you code for 20 amino acids with only 4 nucleotide bases (,U,,)? mrn codes for s in triplets DN mrn U U UU U? codon rg Valsn lays la racking the code rick Nirenberg & Khorana determined 3-letter (triplet) codon system W H Y DIDHERED B EHEFR Nirenberg (47) & Khorana (17) determined mrn amino acid match added fabricated mrn to test tube of ribosomes, trn & amino acids created artificial UUUUU mrn found that UUU coded for phenylalanine (phe) Marshall Nirenberg Har Khorana PDF reated with deskpdf PDF Writer - rial :: 6

7 Division ve. High School he code ode for LL life! strongest support for a common origin for all life ode is redundant several codons for each amino acid 3rd base wobble Why is the wobble good? Start codon U methionine Stop codons U, U, U How are the codons matched to amino acids? 3 5 DN mrn trn amino acid 5 3 U U UU U 3 5 U rg U Val codon anti-codon From gene to DN transcription mrn translation ribosome ransfer RN structure lover leaf structure anticodon on clover leaf end amino acid attached on 3 end nucleus cytoplasm Loading trn minoacyl trn synthetase enzyme which bonds amino acid to trn bond requires energy P MP energy stored in trn-amino acid bond unstable so it can release amino acid at ribosome easily activating enzyme trn rp rp =O rp =O rp OH H 2 O OH O O anticodon tryptophan attached to trn rp U =O mrn trn rp binds to U condon of mrn Ribosomes Facilitate coupling of trn anticodon to mrn codon organelle or enzyme? Structure ribosomal RN (rrn) & s 2 s large small E P PDF reated with deskpdf PDF Writer - rial :: 7

8 Division ve. High School Ribosomes site (aminoacyl-trn site) holds trn carrying next amino acid to be added to chain P site (peptidyl-trn site) holds trn carrying growing polypeptide chain E site (exit site) empty trn leaves ribosome from exit site E U U P Building a polypeptide Initiation brings together mrn, ribosome s, initiator trn Elongation adding amino acids based on codon sequence ermination end codon Leu trn Leu Leu Leu U U U U U U U mrn UU U U U E P U U U U Val Ser la rp UU release factor Protein targeting Signal peptide address label start of a secretory pathway Destinations: secretion nucleus mitochondria chloroplasts cell membrane cytoplasm etc an you tell the story? DN pre-mrn large ribosomal exon mature mrn poly tail RN polymerase cap intron polypeptide amino acids trn aminoacyl trn synthetase small ribosomal E P trn ribosome ot Questions? an I translate that for you? Substitute Slides for Student Print version PDF reated with deskpdf PDF Writer - rial :: 8

9 Division ve. High School an you tell the story? Extra Slides (used some years & not others) ranslation odons blocks of 3 nucleotides decoded into the sequence of amino acids Building Proteins Organelles involved nucleus ribosomes endoplasmic reticulum (ER) olgi apparatus vesicles he Protein ssembly Line nucleus ribosome ER olgi apparatus vesicles From nucleus to cytoplasm Where are the genes? genes are on chromosomes in nucleus Where are s synthesized? s made in cytoplasm by ribosomes How does the information get from DN in nucleus to cytoplasm? messenger RN lternative splicing lternative mrns produced from same gene when is an intron not an intron different segments treated as exons Starting to get hard to define a gene! nucleus PDF reated with deskpdf PDF Writer - rial :: 9

10 Division ve. High School Domains Modular architecture of many s exons may represent functional units of easier to mix and match in the production of new s? So What is a gene? One gene one enzyme? but not all s are enzymes but all s are coded by genes One gene one? but many s are composed of several polypeptides but each polypeptide has its own gene One gene one polypeptide? but many genes only code for RN (trn, rrn ) One gene one product? but many genes code for more than one product So Where does that leave us?! Defining a gene gene gene Defining a gene is problematic because one gene can code for several products, some genes code only for RN, two genes can overlap, and there are many other complications. RN polypeptide 1 polypeptide 2 polypeptide 3 Elizabeth Pennisi, Science 2003 It s hard to hunt for wabbits, if you don t know what a wabbit looks like. human genome Y 3.2 billion bases he ranscriptional unit (gene?) enhancer b 20-30b RN polymerase DN promoter UR translation start transcription start exons transcriptional unit introns translation stop UR transcription stop DN ny Questions?? What color would a smurf turn if he held his breath? pre-mrn P mature mrn PDF reated with deskpdf PDF Writer - rial :: 10

11 Division ve. High School he ranscriptional unit Discovery of Split genes enhancer b 20-30b exons RN polymerase transcriptional unit DN introns Richard Roberts SHL Philip Sharp MI adenovirus common cold beta-thalassemia Splicing must be accurate No room for mistakes! splicing must be exactly accurate a single base added or lost throws off the reading frame U U U U U U U U U U U U rg Ser sp Lys ly His U U U U U U U U U U U U rg Val rg SOP Splicing enzymes snrnps small nuclear RN s Spliceosome exon several snrnps recognize splice site sequence cut & paste No, not smurfs! snurps snrn intron snrnps exon exon mature mrn Whoa! I think we just broke a biological rule! exon spliceosome lariat excised intron Ribozyme RN as ribozyme some mrn can even splice itself RN as enzyme Sidney ltman Yale homas ech U of olorado PDF reated with deskpdf PDF Writer - rial :: 11